How They're Related:
At their core, all three represent transparency or visibility — areas of an image that are visible, hidden, or partially visible. The difference is how they’re stored, edited, and used.
A selection (marching ants) defines which part of the image is editable. The ants march around the area that is 50%+ selected.
Save a selection to turn them into channels or masks.
Channels = Saved Selections
An alpha channel is a grayscale channel that stores a saved selection.
You can convert any selection into an alpha channel and reuse it later.
Masks – Selections That Control Visibility
A mask is a channel linked to a layer.
It hides or reveals parts of the layer non-destructively.
Black on the mask = fully hidden
White on the mask = fully visible
Gray on the mask = semi-transparent
Analogies
Selection = making a temporary stencil.
“Alpha” Channel = saving that stencil as a reusable sheet.
Mask = applying that stencil to a specific layer to control what shows.
Make a selection → Save as alpha channel.
Load the channel → Apply as a layer mask.
Edit the mask using brushes or gradients for advanced blending.