What's the Difference Between Proof Images and Final Images?

I've had a few people tell me recently that they weren't sure what the important difference was between proof images and final images. Here's one example, taken from a recent family portrait shoot at Hovander Park.

The top image is the final image. For this series (which will be posted soon) I chose to go with an antique toning that I thought complimented the stormy weather, farm buildings, and fall leaves. In addition to tweaking contrast and lightness, I also removed the distracting element below the girls and added a vignette to draw the eye to the girls.

I'll post some more examples in the coming weeks.