Trailers are a form of marketing used to promote films and raise awareness by informing potential audiences about the genre, plot, and stars. They are typically shown in cinemas, TV, and online to target audiences that align with the film's genre, such as teenagers, couples, or families. Effective trailers highlight unique selling points to generate interest and encourage viewers to see the film by playing on familiar elements but also including new information. The timing of trailer releases is important to build excitement without allowing interest to fade before the film's release.