Boric acid, also called boracic acid, is a chemical compound, a mild acid often used as an antiseptic, insecticide, flame retardant, and a component of other chemical compounds. It exists in the form of colorless crystals or a white powder and dissolves in water. It has the chemical formula H3BO3 and is known by the chemical name hydrogen orthoborate.
For details of its chemistry, see http://www.encyclopedia.com/html/b1/boricaci.asp.
It can be used as an antiseptic only for minor burns or cuts and is sometimes used in dressings or salves or is applied in a very dilute solution as an eye wash. It is poisonous if taken internally or inhaled, although it is generally not considered to be much more toxic than table salt (based on its LD50 rating of 2660).
It is often used as a relatively nontoxic insecticide, for killing cockroaches, termites, fire ants, fleas, and many other insects. It can be used directly in powdered form for fleas and cockroaches, or mixed with sugar for ants. It is also a component of many commercial insecticides.
Borates including boric acid have been used since the time of the Greeks for cleaning, preserving food, and other activites.
The largest source of borates in the world is an open-pit mine in Death Valley, California, USA.