Genre, from the french term genre meaning 'kind' or 'soft' a term used for any category of literature, as well as various other forms of art or culture e.g. music, films, etc...
Genre is putting things into categories because its useful in any form of study; it’s a way of establishing some kind of control over a mass of information. Genre provides a means to classify certain forms of media like Television, Film, Magazine, etc.... some types of genres are Rom-com, (Romantic Comedy) Action, Sci-Fi, (Science Fiction) Horror. But there are many many more.
A genre is more expectations in a certain type of area rather than what must be in it for example a rom-com film or tv-show we expect to contain 2 stages of, girl/boy completly depressed then girl meets boy ( or other way round)falls madly in love, some kind downfall happens they get separated, they over come their problems and live happly ever after. Though these are in most romance and rom-com films and tv-shows they aren't in them all, instead we expect this to happen in most. Its hard to put every single film into a specific genre because not all fit into one single genre.