A novel is an invented story about a series of connected events in the lives of a group of people.
What sets it apart from a short story is that it is longer, more complex, and deals with more than one issue in the lives of its characters. What sets it apart from a play is that it is not confined by the restrictions of the stage, human actors and the audience. What sets it apart from poetry is that it is written in prose form.
The "Tale of Genji", by Murasaki Shikibu (a Japanese noblewoman), was written in the early eleventh century and is usually considered to be the world's first novel, though many Greek and Latin narratives may also fit that description, including The Golden Ass by Apuleius, a 2nd century Latin author from North Africa.
The novel comes in innumerable genres. Some of the most popular ones are: