It's basically a dialog tree editor which allows you to easily set up dialog flows, flag what conditions there are for showing a certain dialog node and allows you to execute certain actions per dialog node. For each dialog node, there's a whole bunch of things you can do like set up the animations, camera movements, audio, lipsynch etc... in an adobe premiere like fashion (i.e. you have multiple timelines on which you can trigger specific events that control certain aspects of the scene being shown)
