Genre is any style or form of communication in any mode (written, spoken, digital, artistic, etc.) with socially agreed-upon conventions developed over time. In popular usage, it normally describes a category of literature, music, or other forms of art or entertainment, based on some set of stylistic criteria.
Often, works fit into multiple genres by way of borrowing and recombining these conventions. Stand-alone texts, works, or pieces of communication may have individual styles, but genres are amalgams of these texts based on agreed-upon or socially inferred conventions. Some genres may have rigid, strictly adhered-to guidelines, while others may show great flexibility.