What's a Brief ?
Briefs have various different styles usually with a waistband attached to fabric that runs along the pelvis to the crotch and buttocks and are worn by both men and women. See swim briefs for the case of briefs as swimwear.
History of Briefs
Classic briefs were first sold on January 19, 1935, by Coopers, Inc., in Chicago, Illinois, at Marshall Field's department store. They dubbed the new undergarment the "Jockey" because it offered a similar degree of support as the jockstrap (one style of which is also called jock brief or support briefs). The designer of the new style was reportedly inspired by a postcard he had received from a friend visiting the French Riviera depicting a man in a very short, form-fitting bathing suit. 30,000 pairs were sold within three months of their introduction.
In North America, "jockey shorts" or "jockeys" became an often used generic term for men's briefs. More recently, "tighty-whiteys" has become a commonly used slang term for such briefs.
In the UK, briefs were first sold in 1938. Soon, shops were selling 3,000 pairs of briefs per week. They were so popular that in 1948, every member of the British Olympic team was given a free pair of briefs.
In the UK, the term "jockeys" has not caught on and briefs are often referred to as "Y-fronts" or simply "pants". The term derives from the genericized trademark "Y-Front", property of Jockey International. It in turn derives from the inverted Y-shape formed by the seams at the front of the underpants. The colloquialism is used even when the fly opening may differ in style, and not actually form the shape of the inverted letter "Y" fly on Coopers Jockey brand briefs.
In Australia, briefs are referred to as "jocks" but should not be confused with jockstraps (more specifically used by athletes) which expose the buttocks. Australians generally use the word “briefs” to refer to the bikini-style underwear for men, which do not have the Y-front opening.
Since the end of the 20th century, a hybrid called boxer briefs has become popular. Like boxers, they have short legs, but like briefs, they are made of elastic, snug-fitting material. A shorter version of boxer briefs are called trunks.
Design of Briefs
Traditional size briefs for both sexes cover the upper part of the thigh and extend upward up to (or cover, depending on the design) the navel at the waistband. This style is often referred to as "full rise" or "full cut". There are also "low rise" and "mid rise" styles whose measurements vary between manufacturers.
Men's briefs often feature a fly—a covered opening on the front of the garment which allows for convenience in urinating. There are several different fly designs in common use, including the standard vertical fly, the horizontal fly, the Y-front fly, and others. The use of a fly is optional, and many styles do not utilize a fly at all.
Source : Briefs Wikipedia