Technically is a Hormone. It promotes sleep. Is generated automatically in the brain when is dark and is suppresed by light. (That's why you should allways try to make dark when you want to sleep, no TV, computer, etc.)
Depending on where you live, it wouldn't require a prescription to get it. It's nothing like benzos, it's not inducing an artificial sleep, instead it promotes your own natural sleep.
Careful with it, not to take it too long, or your body will not produce it anymore. But i found it very useful in my early weeks.