The foreground tool is used when something is obstructing the structure you are masking eg. Trees, mail boxes, bushes, fences, light bulbs, flowerpots  etc.. The foreground will act as the topmost layer of the design. The foreground tool allows you to mask anything that your visualizer should keep on top of the image. We suggest zooming into the object you want to mask as foreground so you can really concentrate on the details clicking as many times as you need to change direction to define the shape of the object you are trying to make foreground.