PSD format, etc. proprietary format, the program Photoshop can be this format, a large volume compared to the other formats supported in Photoshop dedicated to the. After unlocking a file with this extension notice layers, all the layers of administration, and the like, so you can file that with the PSD format saved changes.
When you open this format in other programs with the shapes you will encounter. PSD format from the layer, the channels and each of the states, RGB color, etc., CMYK, etc. lab color, multichannel, etc. grayscale support.