are 2-3 minute advertisements
made up of film scenes cut out of context. Trailers tend to appeal to specific markets, and if you compare different trailers for the same movie, you'll find that they also portray specific themes depending on their intended market.
The word trailer can also refer to an unpowered vehicle pulled by one with an engine.
Some non-American dialects distinguish a trailer (generally uncovered, used for goods and materials) from a caravan (generally weather-resistant, used for human habitation).
See also Camper, Semi-trailer.