PSD, Adobe Photoshop Document (.psd)
The PSD Raster image file format
PSD files allow graphic designers, producers, and other users to edit images using layers. Layers allow elements to be added and removed easily as well as different filters, effects, transparencies, and more to affect to be applied to an image. PSD files can be opened by various Photoshop programs and they can be flattened to other image formats (PNG, JPEG, GIF, etc) for uploading, sending and saving. Once converted from a PSD to another file type, all layers blended into one single layer. When saved under the PSD file extension the layers are saved, viewable, and can be edited. These files are often used as work-in-progress documents, not for final production and distribution of an image.
Technical details of PSD files
Photoshop files under the PSD file extension store the image while allowing for support of various editing options throughout the Adobe Photoshop programs. Some of these editing options include: masks, transparency, duotone settings, gradients, color balance, blending, clipping paths, and more. PSB files are similar to PSD files but can only support images with height and width up to 300.000 pixels with a length limit of 4 exabytes. Individual layers are saved as opposed to the image as a whole being saved. These proprietary file types are larger, but serve as working documents for graphic design projects. Conversion from PSD to other image types creates a compressed final product.