A missionary is a propagator of religion, often an evangelist or other representative of a religious community who works among those outside of that community. The English word "missionary" is derived from Latin, the equivalent of the Greek-derived word, "apostle".
A parish is a subdivision of a diocese or bishopric within the Roman Catholic church, the Anglican Communion, the Eastern Orthodox Church, the Church of Sweden, and of some other churches. A parish is also a geographical subdivision used in several parts of the world, ... (See: Parish)
Since the Lausanne Congress of 1974, a widely accepted definition of a Christian mission has been "to form a viable indigenous church-planting movement." This definition is motivated by theological analyses of the acts required to enhance God's reputation (usually translated as "glory" or "honor"). The definition is claimed to summarize the acts of Jesus' ministry, which is taken as a model for all minstries. The motivation is said to be God's will, plainly stated throughout the Bible, including the Old Testament.
According to the documents of the Lausanne Committee for World Evangelization, the Biblical authority for missions begins quite early in Genesis, 12:1-3, in which Abraham is blessed so that through him and his descendants, all the "peoples" of the world would be blessed. Others point to God's wish, often expressed in the Bible, that all peoples of the earth would worship Him. Therefore, Christian missions go where worship is not, in order to bring worship to God...
See also: Christian Mission
In ancient times, the Hebrew patriarch Abraham and his wife Sarah were considered to be the prime role-models of "converting" the masses to Monotheism as based on the verse in the Book of Genesis: "God said to Abram, 'Go away from your land, from your birthplace, and from your father's house, to the land that I will show you'...Abram took his wife Sarai, his nephew Lot, and all their belongings, as well as the people they had gathered, and they left, heading toward Canaan..."  (Genesis 12:1;5). "[T]he people they had gathered" is interpreted to mean the people whom Abraham and Sarah had brought over to the belief in the Hebrew God worshiped by Abraham and Sarah themselves.
In modern times, Jewish teachers repudiate proselytization. One basic argument is that all people have the law of God in their heart to a limited degree, and that to teach them more would be to make them responsible for more than Jewish law requires of them. That is, they would start as virtuous gentiles, protected by their lack of formal Torah observance, but after contact with Jewish teachings they would be in held accountable to a higher Jewish religious standard. Non-Jews are therefore encouraged to observe the universal "Seven Noahide Laws" through which they can attain all their pre-destined goals in the world during their entire lifetimes.
However, most Jewish religious groups encourage "Outreach" to Jews alienated from their own heritage due to assimilation and intermarriage. The over-all movement seeks to encourage Jews to become more religiously observant of Jewish law (known as halakha), and those people who do become religious are known as Baal teshuvas. The large Hasidic Judaism group known as Chabad Lubavitch have been at the forefront of such efforts internationally. There are others, such as the National Jewish Outreach Program that do the same on a large scale in North America.
In recent times, the Reform Judaism movement has begun an active program to convert to Judaism the non-Jewish spouses of its intermarried members as well as to activley seek and encourage non-Jews who have an interest in Judaism to become Jews, the rationale being that Jews have lost so many of their own during the Holocaust so any newcomers must be sought out and welcomed. This approach has been repudiated by the Orthodox Judaism and Conservative Judaism wings as being unrealistic and as posing a danger by making Judaism seem as an easy religion to join and observe when in reality being Jewish entails many difficulties and sacrifices.
Jehovah's Witness missionaries
Jehovah's Witnesses are known for their missionary activities. Typically, all adult Witnesses are expected to spend a certain amount of time every week "witnessing" to those in their area. Depending on rules in the country, this can take the form of going from door to door talking about their religion or standing in a public place holding up magazines (The Watchtower and Awake!) and responding to questions by passers-by but not soliciting contact themselves.
Missionaries take on a special work, such as publishing in remote areas. This requires committing to at least 130 hours in the public ministry. To prepare them for this, a special training course is provided annually for Jehovah's Witnesses who have proven an ability to perform this service.
Several years of pioneer service is required, especially in areas where special need of publishers is great. The requirements are challenging because Jehovah's Witnesses do not receive salaries for their minsterial work. A Pioneer would need to be self sufficient, working part or full time while fulfilling ministerial obligations. This prepares them for the reality of missionary work in "Third world" lands where they would need to provide for their own needs while organizing congregations.
The Church of Jesus Christ of Latter-day Saints is one of the most active modern practitioners of missionary work.
Young men between the ages of 19 and 26 who are "worthy," or following church teachings, are strongly encouraged to go on a two-year, full-time proselyting mission. Young women, who must be at least 21, may also serve 18-month missions. Elderly, retired couples are encouraged to serve missions as well, but their length of service varies from 12 to 24 months. The Church has about 60,000 missionaries worldwide. 
Prospective missionaries receive a "call to serve"—an official notification of their location assignment—through the mail from the president of the Church and are "set apart" (specially assigned through a priesthood blessing) to preach the gospel. Young men are also ordained Elders if they have not been already. Missionaries generally stay in the same general location for their entire mission. They are, however, relocated within this region every few months. This area is called a "mission" and is an official geographical area recognized and administered by the Church.
Missionaries pay their own expenses, usually with assistance from family and friends. Missionaries who cannot raise the needed funds may obtain assistance from a fund operated by the church and contributed to by members. In the past, each missionary paid his or her actual living expenses, but this approach created large burdens on missionaries who served in expensive areas of the world, so in 1990 a new program was introduced to equalize the burdens. Now, all young missionaires pay a flat monthly rate which is distributed according to regional costs of living. The current cost of a mission is approximately $400 per month, which covers food, lodging, transportation, and personal items. Young people in the church are encouraged to save money throughout their teenage years to pay as much of this as they can, although nearly all receive assistance from family (usually parents) and friends. In some cases, the general missionary fund is used to pay for missionaries' expenses, but the church discourages relying on this fund and prefers missionaries to pay their missions themselves (this particular church fund is made up of contributions from church membership and monies are generally not taken from tithing or other Church funds). Elderly couple missionaries pay their own costs.
Newly called missionaries attend a short training period at one of the nearly two dozen Church Missionary Training Centers (MTCs). The largest MTC is located in Provo, Utah adjacent to Brigham Young University (BYU). Missionaries serving English-speaking missions spend three weeks at the MTC and are trained in the use of proselytizing materials and taught expected conduct. Missionaries bound for foreign-language missions spend longer periods at the MTC—eight to ten weeks—in order to learn the language. During this period, they are encouraged not to speak in their native tongue but rather to immerse themselves in the new language. Other MTC campuses exist in other parts of the world for missionaries serving in their native countries outside the US.
MTCs and their teaching methods have reportedly been studied by various organizations because of the rapid ability of the missionaries to learn a foreign language in the setting. Occasionally, missionaries are said to be fluent in the language they study at the end of the eight- to ten-week period.
Full-time proselyting missionaries are required to adhere to a dress code: for men, dark trousers and suit coats (which are optional in hot climates), white dress shirts, and ties are required; for women, modest and professional dresses or blouses and skirts must be worn. Casual clothes may be worn when providing manual labor or during "preparation day" (called "P-day" by missionaries) when the missionaries recreate and do their cleaning, shopping, and laundry. All full-time missionaries wear a name tag that gives their surname with the appropriate title ("Elder" or "Sister" in English-speaking areas) and bears the church's name.
In the past, church officials expected young men to serve missions regardless of marital status. Today, however, young married men are not expected to serve missions, unless specifically invited by leadership to oversee a mission as a mission president. This call is typically extended to the couple, and in turn, the entire family.
Older, retired couples are also encouraged to serve missions and may serve as long as they desire (typically from one to two years). Many older couples have been known to serve several consecutive missions, which may include proselytizing, service, or historical/historical re-enactment temple work or to fulfil various other needs of the Church.
Besides the above-categorized missionaries, the LDS Church also has a strong welfare missionary program. The missionaries who serve these types of missions typically serve in poor and third world countries and do not actively proselytize. Regular proselytizing missionaries typically engage in welfare activities and community service for a few hours a week.
Completing a mission is often seen as a rite of passage or crucible for young LDS men, and most tend to regard it as a positive event: The phrase "the best two years of my life" is nearly a cliche among returned missionaries when describing their experience.
It is perhaps unsurprising, however, that with many thousands of young men acting as missionaries, that some have negative experiences or regard their missionary tenure poorly. Some report that they serve missions not out of genuine desire to do so but due to peer pressure or due to cultural and familial expectations.
The most visible missionaries are typically those who proselyte door-to-door and ride bicycles for transportation, but not all missionaries engage in these activities. There are "service missionaries" who solely volunteer in impoverished areas, do genealogical research, and/or are tour guides or hosts. In many areas, even proselytizing missionaries spend most of their day responding to incoming phone calls, queries, etc., and use public transit or drive automobiles owned by the Church.