In literary terms, a conceit is a device used in order to make a story more accessible to the audience. A simple example of this is the film Speed. In Speed, Sandra Bullock's character is a workaholic that can not slow her life down. She is also stuck on a bus that she can not slow down (or it will explode). Since the audience, obviously, has never been in such a bus, the film-goers can not directly sympathize with the protagonist (Bullock's character). The conceit, however, enables the audience to do so because most people have had a job, friend, lover or hobby that he or she has become obsessive or otherwise spent too much time on. As the audience has struggled with a too-fast life, so can they sympathize with a character stuck on a too-fast bus.
