Trap shooting is one of the three major forms of competitive clay pigeon shooting (shotgun shooting at clay targets). The others are Skeet shooting and sporting clays. There are many versions including Olympic Trap, Double Trap (which is also an Olympic event), Down-The-Line, and Nordic Trap. American Trap is most popular in the United States and Canada. American Trap has two independent governing bodies: the Amateur Trapshooting Association, which sanctions shoots throughout the United States and Canada, and the Pacific International Trapshooting Association, which sanctions shoots on the West Coast.
The sport is in some ways a replacement for a game where the targets were live pigeons. Indeed, one of the names for the clay targets used in shooting games is clay pigeons. The layout of modern trap shooting is different from skeet shooting in that there is only one house that releases targets and the shooters only move through 5 different positions.
Trap shooting has been a sport since at least 1793 when it used real birds, usually the Passenger Pigeon, which was extremely abundant at the time. Fake birds were introduced around the time of the American Civil War as the Passenger Pigeon was nearing extinction and sufficient numbers were not reliably available. Clay targets were introduced in the 1880’s.
From Wikipedia: http://en.wikipedia.org/wiki/Trap_shooting