Photoshop provides a very quick and easy way to make a temporary mask that can, in fact, be edited. It's called Quick Mask, and one of its advantages is that you can see both the image and the mask at the same time. You can start with a selected area and use the painting tools to add to it or take away from it, or you can create the mask entirely in Quick Mask mode. Let's apply a Quick Mask to an image.
Try it Yourself
Create a Quick Mask
Quick Masks are a great time-saver, as you'll soon see. Follow along to try them.