Clicking with 
unions the newly created fill with the previous selection.
drag | Fill from each point |
From each point, the fill spreads to the neighbors with the colors similar to that point. This can be used to fill an area currently filled with a gradient or blur.
From each point, the fill spreads to the neighbors with the colors similar to the initial point of the drag. This can be used to fill several disjoint bounded areas by starting in one and dragging over all of the areas.
-clicking an object sets its fill (or stroke with ) to the tool’s current style; the object need not be selected.