Masks are areas you select that you don't want to be affected by filters or something. As well, you can invert your mask so that whatever you do, it ONLY affects a certain part of an image [img]smile.gif[/img] In Photoshop,you turn on Quick Mask Mode (Ctrl+Q) and you use the brush tool to paint on wherever you don't want selected and it looks like you painted translucent red over it then you turn off Mask Mode (Crtl+Q again) and whereever you didn't paint will be selected, it's kinda like putting masking tape over certain parts of a wall before painting it [img]smile.gif[/img]