Being induced with a gel? How does it work?

So my doctor said i was going to come in Tuesday night for preparation. He said they would insert a gel, and then remove it later and start me on the pitocin drip(not sure if that's how you spell it) he said that the gel alone could cause contractions. So my question is, how does the gel work? And does it hurt? And have you ever been induced this way, whats the purpose of the gel if their going to put me on pitocin anyway?