Q: how do i determine what kind of computer i own?

To see which model you have go to the Apple in the upper left corner and select About This Mac, then click on More Info (and then System Report if you’re running 10.7 Lion or 10.8 Mountain Lion). When System Profiler comes up check the Model Identifier and post it back here.

Open System Profiler in the Utilities folder. It will provide the relevant information.