I selected an area from a mask, when I hit delete key, it just paints that area as white. If I select whole canvas and hit delete, the whole area gets white. All I want to do is delete the selected area from the mask. I remember I could do that previously. So my best guess is I turned some options on/off that is preventing me from doing that. Please help me out.
From Star Wars A New Hope: "It's a trap!"
Actually it's a mask. A mask uses white for "full effect" and black for "no effect" with grays for "partial effect." If you use a selection when creating the mask, the selection becomes white, with black for everything outside the selection. You can't really delete parts of the mask, you just turn them on or off.