What is going on with the bottom of my MacBook?

I bought a MacBook in March 2010. The bottom on it is different from older ones, it’s not plastic but….god I can’t think of what you would call it. If you have a new MacBook you probably know what I’m talking about but anyhow it’s bubbling….like, it’s coming unattached from the bottom of the computer and….bubbling. Big bubbles. I really don’t know how to explain this….does anyone else have this problem? Can it be fixed? I think my warranty was only for a year…..