What is a trailer?

Who has not watched a movie preview (lasts between one and three minutes) before, and awoken his curiosity to run to the cinema’s premiere once it was released? How many TV spots (lasts less than a minute) of the latest video games have not lured fans to the store? How about those commercials advertising the newest car, event or dish on a restaurant menu? Whichever form it takes, or whatever its purpose, trailers or teasers are extracts from films, video games, or TV shows such as sitcoms and dramas, which are intended to promote the same.