The Area ID is for the Rocket Turtle, a boss that was never finished. The Rocket Turtle flies to each Area ID in the order you specify. After flying through all of them, the Rocket Turtle flies up to the upper-left corner of the level.

As for a list of events, you can open the Find/Replace dialog for a list of events, but for what they actually do, I'm not sure where to get that. Best to experiment. However, there is a large amount of articles on this site that talk about various things that JCS can do.