Distinction among the three varieties of Undos

[hieadfond]

I searched for documentation on the three sorts of undos in retouching: brush, stroke, and point.
Could someone perhapsspace bar clicker guide me to documentation on the distinctions between these?
Thanks

[Catherine]

"Undo brush" reverts all changes made with the current brush (clicking a second time will revert the previously selected brush and so on).
A stroke is everything you draw with the left mouse button pressed. Releasing the button ends a stroke.
A point is the smallest unit of brush application, a stroke contains one or more points.