Just what is meant by "artificial intelligence"?

It has only been in recent years that we've come to see artificial intelligence as a reality and not something out of a science fiction story. Even now, we're still struggling to come up with an adequate definition of the term "artificial intelligence" which isn't surprising when you consider that after thousands of years, humans can't even decide on a definition for "intelligence." Put one way, artificial intelligence is a term given to computer systems that attempt to simulate human intelligence and learning. But even that definition is too big to wrap your head around. To simplify it, you can break artificial intelligence into two categories: Strong (or broad) AI, and weak (or narrow) AI.