A demo to go with an explanation.
The histogram plugin ordinarily applies a value for a single frame. This new feature modifies histogram to show values for a selection of frames. You use several frames in a video that you want to use the "average" color to determine the color you want the rest of the video to be. When there is a large light or color variation within a range of a few frames, you spend a lot of time correcting each frame when it would be better to just get an average value to use. If you want, then you can make a LUT for that set of frames instead of each frame.