Deploybot is a tool for doing continuous deployment.

Continuous deployment is the tool of putting software in production automatically as it is developed, as opposed to working towards a release milestone and doing that deployment manually.

It's comparable to continuous integration, except that most CI installations only involve automated builds and test runs. Some people have extended this with deployment. That's probably a great idea, but usually executed in a mostly ad-hoc fashion. Deploybot's goal is to alleviate that.