A server is "different" not better than a client. Imagine a game of UT.
One person serves. Sometimes they run a listen server and they also play but for the big servers they don't. All the rest are clients. They connect to the server. However the clients don't connect to one another.

You can use a client to put stuff on a server, however the server can't put anything anywhere. It just acts as a server.

You'll want a client if you want to download from other people. And a server if you want others to download off you.