Snapshots as shown in Figure 2 is a lot like the photo states in the History palette of Photoshop. It records or saves the state or condition of an image at certain points in your adjustments. You can record these Snapshots of any image as seen in the central work area. This can be when you have reached a certain stage in the process that you want to remember or you can go back to the History, click on a certain point there, and record that adjustment as a Snapshot.

Figure 2: Snapshots is similar to the photo states in the History palette of Photoshop.
Snapshots is not just about remembering your adjustments. You can also use this as a very powerful tool to try out different adjustments on a photo and compare them (Virtual Copies are another way of remembering different adjustments). Here are some tips for doing that:
For more information about Photoshop Lightroom, see the following: