See the wiki pages: Shelving and Checkpointing
When working on a collection of local changes, it is sometimes desirable to be able to checkpoint your work. The utility, of course, it not in the checkpointing, but in the fact that you can then restore the working copy to one of your previous checkpoints. Workarounds today generally come in the form of temporary branches (which aren't offline) or series of patchfiles. Subversion should offer a first-class feature to facilitate this use case.