I got a confused comment a few minutes ago and realized that apparently, I never actually explained what NaNoWriMo was. Well then.
nanowrimo.org <-- That is the NaNo site, it has more details and lets you sign up and stuff. I'm just here to tell you the basics.
NaNoWriMo stands for National Novel Writing Month, but we usually shorten it to NaNoWriMo or just NaNo. It takes place in November, every year, and it's just a thing where tons and tons of writers from around the world write novels at the same time.
The NaNo definition of a "novel" is a "lengthy work of fiction." By lengthy they mean 50,000 words long, or longer if you're ambitious.
To be doing NaNo "by the book" you start with a new idea and write what would be published as a novel, counting only words written in November. However, there is no rule against writing poem collections or a recipe book or whatever. That just makes you a rebel, and that is not discouraged. They even get their own forum.
If you have further questions, I refer you to the NaNo FAQ page. http://nanowrimo.org/faq
I hope this answered any questions.