Triple Sec is a type of orange liqueur that was derived from Curaçao, a liqueur made from sun dried native orange peels on the island of Curaçao. Triple Sec was invented in 1834 by Jean-Baptiste Combier, a distiller in Saumur, France. Combier still makes the original Triple Sec recipe, which calls for three distillations, and is drier than the original Curaçao, at 80 proof.
Today, orange liqueurs that are labelled Triple Sec are clear and taste primarily of oranges. Interestingly enough, both Cointreau and Grand Marnier once called themselves Triple Sec, though they no longer do. Some common brands of Triple Sec are the aforementioned Cointreau, Citronge (made by Patron), Triplum (from Luxardo), Hiram Walker, and Bols.
Generic Triple Sec is usually inexpensive, low quality, very sweet, and artificially flavored.