Romantic comedy convention

In the trailer we can see that the target audience of romantic comedy films is young teenagers, it is usually girls. In beginning of trailer we can see that Hugh Grant and his silly friend  having conversation  in the library, where the Julia Roberts hiding behind books wearing sun glasses and pretending reading a book. The next scene is that Hugh finishes his conversation with his friend and starts talking with Julia. Couple talk about their love interests with some funny jokes, to show audience the genre of the film.