Specify whether to create a new selection, add to an existing selection, subtract from a selection, or select an area intersected by other selections.
To soften the selection border so that it blends into the area outside the selection, enter a Feather value.
To smooth the edges of your selection, select Anti-aliased.
To add to the selection, release the mouse
button; then press Shift and, when the pointer changes to , drag.
To subtract from the selection, release the mouse
button; then press Option and when the pointer changes to , drag.
To add straight-edge segments, press Option (while
pressing the mouse); then release the mouse button and, when the
pointer changes to , click
where you want to position the end of the segment.