What is the Mac?

I didn't know what the Mac is until I was a junior high school student. When I was a high school student, I knew that the Mac was the computer of the Apple Inc. But I had never seen it yet. When I took the train and got the seat, a man who sat next to me used the computer which I had never seen before and it was the Apple Computer, so it was my first time to see the Apple Computer. Now I know what is the Mac. But I don't know its detail, the way to use, and the diffrence between the Mac and the Windows.