A clay pigeon is a frisbee-shaped target used in the sports of skeet shooting, trap shooting and also for training in rifle shooting (in this case they are not thrown, they are just placed on a convenient berm).
Clay pigeons are thrown into the sky by catapult-like machines that use springs and levers. Serious ranges use large automated machines that can have over one hundred skeets loaded in a series of hoppers.
Clay pigeons (also called clays) are not made of clay - actually they are made of marble dust bound together with vegetable pitch. They are normally painted in bright colors, like blaze orange, and they are very brittle - they will smash if dropped on the floor from 3 feet.
The diameter ranges from 6 to 10 centimeters and the weight varies from 100 to 30 grams (for various applications). While the Olympic trap and skeet competition uses only the standard target, in other disciplines you find also the following types: rocket, rabbit, battue, midi and the really microscopic minis.
Who invented it anyway?: in 1880, at a time of great popularity for pigeon shooting, American inventor George Ligowski had the brilliant idea of producing modeled clay disks.
More than you ever wanted to know about the sport at: http://www.sportingclays.net/