Action commands can be useful for repetitive tasks such as resizing or save-for-web.

Active Layer
When creating multiple layers, the active layer is the ONLY one that can be edited by your actions.

Adjustment Layer
This lets you apply colour and tonal adjustments to an image, without making any permanent changes. You can use this kind of layer to experiment with colours and tones – think of it as veil over the underlying layers.

Aliasing & anti-aliasing
Aliasing = when the resolution of an image is too low and the edges are jagged.
Anti-Aliasing = smoothing the jagged edges by averaging the colours of the pixels at the edge of an image.

Application Bar
The bar that contains menus and commonly used tools to help you manage your workspace.