When changes are made to the working copy, they can be uploaded to the repository. Subversion works by setting up a central repository on a server or local computer that every user connects to and downloads a personal working copy from. It is written primarly for Mac OS X users, but since Subversion itself works the same on all platforms, most of this tutorial should apply to Linux or Windows users, too.
This tutorial explains the basics from installing subversion and getting started to working with other people on the same project.