Subversion doesn't distinguish between filesystem space and “branch” space; branches and tags are ordinary directories within the filesystem. This is probably the single biggest mental hurdle a CVS user will need to climb. Read all about it in Chapter 4.
Since Subversion treats branches and tags as ordinary directories, always remember to check out the trunk (http://svn.example.com/repos/calc/trunk/) of your project, and not the project itself (http://svn.example.com/repos/calc/). If you make the mistake of checking out the project itself, you'll wind up with a working copy that contains a copy of your project for every branch and tag you have.[43]