If you don’t know what it is the distributed source control system, you should visit the Joel Spolsky site.
“Mercurial is better than Subversion.
It is a better way of working on source code with a team. It is a better way of working on source code by yourself.
It is just better.
And, mark my words, if you understand the way Mercurial works, and you work the way Mercurial works, and you don’t try to fight it, and you don’t try to do things the old Subversion way using Mercurial but instead you learn to work the way Mercurial expects you to work, you will be happy, successful, and well-fed, and you’ll always be able to find the remote control to the TV.”