Interfaces... What's the deal?

Question

This is a newbie question. I do not understand the whole idea of the interface thing. It is my understanding that an interface is basically just an abstract class with abstract methods that all have to be implemented in the class that implements them. So, if you have to implement all of these properties and methods on the class implementing the interface anyway, what is the point of having an interface, other that the fact that the new properties and methods will show up in your auto-complete in Visual Studios. If this is all an interface is, how does that replace multiple inheritance? Any insight would be appreciated. -agartee