Lightroom's Snapshots panel tends to go unnoticed by many Lightroom users, but I find it an incredibly useful feature. Basically, a "snapshot" is a version of your image that you like and way want to revert back to later on. After you've made a snapshot of your image, you can continue to experiment with different develop settings, knowing that you can always go back to the version you liked.

This video demonstrates some of the basics in working with the Snapshots panel in Lightroom. Be sure and read the full article at thelightroomlab.com/2008/12/creating-snapshots-in-lightroom/