Servers in Applications
 

I am relatively new to Linux. When an application asks for a server that is needed, 1) where do I find a server? 2) What does it do? 3) How does it work?

There are a lot of servers: web server (for instance apache), database server (msql, etc.), mail server, etc.
If an application asks for a server, you should find in the documentation what kind of server it needs.

Have a look here