The
command adds an alpha channel to the selected layers. The alpha channel represents the transparency of a layer.Most layers, except the background layer, usually already have an alpha channel, unless it was imported from a file format that defined it as not having an alpha channel. For any layer that doesn't have one yet, this command lets you add it. The names of layers that do not have an alpha channel are shown in bold in the Layers Dialog.
You can access this command
From the main menu through
→ → .From the Layers Dialog, you can access it through the command of its context menu.