Almost anyone who has ever had a cat "knows" it speaks to them. Our cats take on personalities and little anthropomorphized lives, but never actually say a word. Some people think our ability to communicate with them is due to a kind of telepathy.
But really something much more basic and comprehensive is actually going on. If you think about what we've learned about behavior, learning, and conditioning it becomes pretty apparent that their way of speaking to us is very much related to rewards like food or affection. But most cats are pretty independent and self-reliant, why communicate, why not just force humans to do what you want like this cat?
Some scientists now believe that beyond simple back and forth communication, cats are actually manipulating us in interesting ways. Again this sort of behavior can be seen as closely related to conditioning, but it is interesting to note the rather ingenious and complex way this happens, particularly with cats.
Scientists have discovered that cats are very sensitive to their owners and work out rather complex relationships with them. These relationships are remarkably similar to the nonverbal relationships mothers have with their babies.
http://www.scientificamerican.com/blog/post.cfm?id=the-manipulative-meow-cats-learn-to-2009-07-13 (there are a few of these, just google!) :)
This makes so much sense to me because we spend so much time with them and they are dependent on us for so much, it seems perfectly logical that they could easily pick up on these verbal cues and become conditioned to communicate in this blatant way. Cats also have a large vocabulary and it wouldn't surprise me if "Fluffy" sounded the cry in one way that'd we'd "know" what she was saying even though it all happens without us even thinking about it. Both the cat and the person have become conditioned to respond with similar vocal sounds, actions, or body language. It's a real give and take, just like most relationships.