Adjustment layers apply color and tone adjustment to your photo non destructively. This means that rather than making an adjustment directly to your photo, you can create a separate layer that will make those adjustments, leaving your original photo untouched.

This command allows you to select a specified color or range of colors. If you want to replace a selection, remember to deselect all before applying the command.

A layer mask is used to hide portions of a layer and reveal portions of whatever layer is below it. You can modify the mask by using the brush tool and painting in either black or white.