What is PSD image file?
Photoshop has ties with other Adobe software for media editing,
animation, and authoring. The .PSD (Photoshop Document),
Photoshop's native format, stores an image with support for most
imaging options available in Photoshop. These include layers with
masks, color spaces, ICC profiles, transparency, text, alpha
channels and spot colors, clipping paths, and duotone settings.
This is in contrast to many other file formats (e.g. .EPS or .GIF)
that restrict content to provide streamlined, predictable
functionality.