System Restore Explorer is, just as its name suggests, a program which will let you take a closer look at your system restore points.
Normally these kind of system-level backups aren't too accessible to most people. You can restore an entire system point, or maybe a shadow copy or two (right-click a folder, select Properties > Previous Versions), but that's about it.
Run System Restore Explorer, though, choose a restore point and click Mount, and it'll be displayed in an Explorer window. You can then browse its files and folders just like any other drive, open and view whatever documents you encounter, even drag and drop files from the restore point window into some other folder.
And once you've finished, clicking the Unmount button will remove the virtual drive. Or you can use the Delete button to wipe a particular restore point altogether (useful in itself as Windows normally only allows you to delete all but the last restore point).
Please note, System Restore Explorer is a beta and likely to contain bugs. We wouldn't recommend you use it for any system-critical purpose unless you have a complete system backup to hand.