Once you've finished making changes, you need to commit them to the repository, but before you do so, it's usually a good idea to take a look at exactly what you've changed. By examining your changes before you commit, you can make a more accurate log message. You may also discover that you've inadvertently changed a file, and this gives you a chance to revert those changes before committing. Additionally, this is a good opportunity to review and scrutinize changes before publishing them. You can see an overview of the changes you've made by using svn status, and dig into the details of those changes by using svn diff.
Subversion has been optimized to help you with this task,
and is able to do many things without communicating with the
repository. In particular, your working copy contains a
hidden cached “pristine” copy of each version
controlled file within the
Because of this, Subversion can quickly show you how your
working files have changed, or even allow you to undo your
changes without contacting the repository.
 And also that you don't have a WAN card. Thought you got us, huh?