The layer is the single most important concept in Photoshop. Picture a stack of transparent sheets: each one carries part of the image, and you see them all together through the transparency.

Why it matters

• You edit one element without touching the others.
• You reorder the stack simply by dragging layers.
• You set the opacity of each one independently.
• You can hide a layer with the eye icon.

The Layers panel

This is your control centre: the top layer appears above all the others. Get into the habit of naming your layers (double-click the name) so you never lose track.

Key point: always work on separate layers. That’s what makes retouching editable and non-destructive.