A rite is an established, ceremonious, usually religious act. Rites fall into three major categories:
Within Christianity it can have a much more specific meaning -- in this sense a rite is a particular liturgy. For example, in the Roman Catholic faith, the sacrament now called the Anointing of the Sick has traditionally known as the last rites, being often performed on someone who is dying.
Freemasonry in North America is divided into the Scottish Rite and the York Rite.