The Instant Alpha tool lets you make parts of a photo transparent in order to remove the photo background.
As you drag, the selection grows to include the contiguous area that uses similar colors. You can control how much of the image is selected by dragging less or more.
You can restore the parts removed from the image at any time. To revert to the original image, choose Format->Remove Instant Alpha. To restore parts of the image removed using Instant Alpha, choose Edit->Undo until the parts have been restored.