As part of my studies I have to go through OSI Reference Model. As far as I understand it's an alternative to TCP/IP. Although, some sites I looked at say that TCP/IP is a part of OSI. It got me confused.

To my best knowlege most of the networking is done using TCP/IP, at least I never met OSI before. Saying that my teacher keeps on pushing OSI to us and all the work given to us includes OSI but doesn't even mention TCP/IP. I personaly think he's in the wrong.

I wanted to know your oppinion on the subject and, if possible, some info?

Which one of these two are wider used?
Which one of them is the one you generaly use?

I'll be very grateful for all your replyes.