There are a few things you need to know if you want to edit a layer mask in GIMP. First, the layer mask is a control that lets you selectively edit the content of a layer. Second, there are three types of masks: basic masks, histograms, and masks with properties. Basic masks are the simplest type and let you select only one part of the image. histograms are more complex but can be used to create more realistic looking images. Finally, masks with properties let you change how the content of the mask is edited (such as opacity).
