During a recent workshop I had some one ask what a Snapshot was (its a panel on the left side in the Develop module). Then everyone else kinda chimed in with a "yeah what the heck is that?". They don't get used a lot, but I think they definitely do come in useful at times.
Basically, a snapshot is a freeze-frame of your photo at that moment in time. It's a way to save all of your develop settings at a certain point in case you ever wanted to revert back to them. So let's say you're working on a photo. You're pretty happy with the way the photo looks but you want to try a couple of other things as well. Sure, you could create a virtual copy (here's a video on how to do that) and try things out on the copy but I find virtual copies better for when you want to compare two different versions of a photo. If I just want to experiment but want an easy way back, create a snapshot first, and have at it. Experiment away, knowing that you can get back to your happy place (the exact settings where you created the snapshot) with just one click in the Snapshots panel.
That's my story for the day. Have a good one.