Shelving (issue #3625) is the ability to put aside an uncommitted change in the WC, as if putting it on a shelf, in order to work on something else, and later bring the change back in to the WC. It is very similar to saving a patch file created by svn diff and later applying it with svn patch.
Checkpointing (issue #3626) is the ability to save a snapshot of an uncommitted change in the WC from time to time, and later restore the working copy to one of those previous snapshots. The implementation is based on letting a shelf contain multiple versions.
Wiki pages related to shelving and checkpointing:
- Shelve-Checkpoint Side Issues — Loosely Related Issues with Subversion
- Shelving and Checkpointing Dev — Local History Operations for Subversion
- Shelving Command-Line UI Design
- Shelving in Svn-trunk — A summary of the Shelving and Checkpointing feature in development for Svn-1.11
- Shelving-v1 in Svn-1.10 — A summary of the Shelving feature added in Subversion 1.10.