The genre may be considered as a practical device for helping any mass medium to produce consistently and efficiently and to relate its production to the expectations of its customers. Since it is also a practical device for enabling individual media users to plan their choices, it can be considered as a mechanism for ordering the relations between the two main parties to mass communication.Dennis McQuail 1987, p. 200

Ed Buscombe notes that the ‘kind’ or ‘type’ of film is usually recognised “and largely determined by the nature of its conventions” (1986 p. 15). In other words, the textual nature of the media production. To understand the way in which textual analysis is used to define the genre of a media product, look at any extract from any film.

A key theoretical area that underpins Media Language is the study of GENRE. Genre is a way of thinking about media production (INSTITUTIONS) and media reception (AUDIENCES). Overall, genre study helps students to think about how media texts are classified, organised and understood, essentially around SIMILARITIES and DIFFERENCE. In that media texts hold similar patterns, codes and conventions that are both PREDICTABLE and EXPECTED, but are also INNOVATIVE and UNEXPECTED. 

Genres are really important for institutions and audiences.

. . . saddled with conventions and stereotypes, formulas and
clichés and all of these limitations were codified in specific genres. This was the very foundation of the studio system and audiences love genre pictures . . .Scorsese, A personal Journey through American Cinema (1995)