Copyright or Trademark

Based on facebook as an example...what have they copyrighted and what have they trademarked? I want to begin an online business but not sure what I need to copyright or trademark... it will be a social networking site...

If the name is suchandsuch.com do I need to copyright suckandsuch.com or just suchandsuch? Also can it be registered as a trademark after I make a logo out of it? It's very confusing...

You can not copyright a name. That is what trademarks are for.
You can have copyright on the site content.

U.S. Copyright Office
United States Patent and Trademark Office

are the two government agencies responsible for Copyright and Trademarks respectively. Both have FAQs you should read before you ask further questions.