Stacking Selections

If you create a new selection on top of an existing selection, the new selection becomes the active selection.

If you create a selection and apply an effect, then create a second selection and apply a different effect, the second effect only acts on the second selection because the first selection is deselected when you make the second selection.

In this example, if you drag the Invert effect down in the stacking order so it is on top of Elliptical Select and you drag the Mosaic effect up so it is above Brightness/Contrast, your image changes as follows:

You can see a selection that is lower than other selections in the stacking order by turning off all selections above it. You can still add effects to the original selection, but to do so, you have to add it to the top of the stack, then drag it down to the appropriate position above the first selection (and below the second).

You can combine multiple selections using the Add, Subtract, and Intersect modes. For more information, see Adding, Subtracting, and Intersecting Selections.