Blending mode controls how the layer interacts with other layers. For example, the blending mode "multiply" looks at the color of your layer and multiplies the base color by the blend color. The result is always a darker color. Multiplying with black results in black, multiplying with white leaves the color unchanged.

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.