IDEs

I don’t understand the purpose of an IDE.

I’ve been trying to work with Apple’s XCode and it seems like a capable little text editor with a whole lot of stuff attached that I have no idea what it does. I do most of my work in emacs or BBedit. I have the feeling that XCode would make espresso for me, if I had half a clue. And people I talk to, like Xris say they have been spoiled by IDEs. What do they do that will spoil me? Help!