I can't type on my MacBook Air?

Up until an hour ago, my computer was working perfectly fine. That is, random numbers automatically began appearing on my Word document while I was tying something out. The numbers had no pattern, they weren't one number in succession. So, I simply shut my computer off and when I turned it back on, I couldn't type a thing. My password has a capital letter in it and when I hit Caps Lock, nothing. The only key that works is the power button. I don't know what to do?