M

mask

The process of defining an area of an image or layer for selection, modification, or transparency.

merge

In the context of layers, merging refers to combining some of the layers in a design while keeping other layers separate.

metadata

Ancillary reference information attached to an image file. Photoshop supports six metadata subcategories: File Properties; EXIF Camera Data; Camera Raw; GPS; Edit History; and project-based IPTC information that shows authorship, assignment information, and other workflow data points.

mode

A way to apply editing and painting techniques. Palettes have Mode drop-down lists.

See also [palette]

multiple views

More than one window opened for a single image file. You can open two separate windows of the same file, specify a high rate of magnification for editing in one window, and leave the other at full screen size to check your progress as you work.