I was in the same boat as you at the very beginning. Experience will work the best for you. My first job I dived in to managing 11 servers. I was fortunate enough be be able to purchase VM ware and virtualize every one of them. The company wanted everything up to date after I got there (upgrade to exchange 2010.. things like that). So with my very first experiece with servers I was exposed to everything. Exchange, SQL, Dynamics AX, Atas, Oasis, FTP, and many more.
It's really simple to think about. A server is just another computer. That's it. It's got a motherboard, processor, and RAM.
A server has programs on it. What program it has on it decides what kind of server it is (there are also server roles.. which decides as well lol.. but forget about that for now).
The reason a server is a server is because instead of one user, there are maybe 200.. or 1000.. or however many users connected to it. So this server has to have, in most cases, two or more processors.. and Lots of ram.
If you don't know what exchange is, look it up. You know what Microsoft Outlook is... Exchange just manages
it. But for the whole company.
Take a "Mail" server, for example. If I made an Exchange Mail server it all it does is manage all of the emails, maybe filter out spam, gives you a pretty admin console where you can search through everyone's and do MUCH more stuff.
All it is is a server (made up of the same hardware of a computer) and a program (Exchange).
I'm not going to go any further as it may be useless... you might not even read this topic again