Genre means in general; just the organization of books, music, and anything else, but it's most commonly used with books. In books there is; fantasy, non-fiction, fiction, science-fiction, and also books about mystery, it's just the way of organizing different kinds of books so that people can say, "Oh! I love fantasy books!" so it's easier to find a book you want.
Genre is the type of music book sport like in music there will be rap,alternative,punk,country etc. Etc. Etc. You understand