PSD is the abbreviation of Photoshop Document. It’s a proprietary, raster graphics format designed as a container for layered image files. Despite Adobe Company doesn’t allow third party developers to work directly with the format standard, they can always add the PSD support for its own digital products.
PSD format will help you to work with layers. You can add a text layer or visual effects over your image background. Such things are indispensable for designers. Besides, your images could be compressed without quality loss. PSD files are very useful especially when you need to create or edit a website layout.
Adobe Photoshop is the best way to open and edit any PSD file. Also, GIMP and Paint.NET can be good solutions if you need to work with PSD files. But you should know that there are some restrictions when you are using non-Adobe graphics editors. They usually related to a file size. Some programs just can’t open large PSD files. And Photoshop hasn’t limitations for importing or exporting of PSD files.
If you don’t need editing tools for PSD files, you can use such utilities as FastStone Image Viewer or IrfanView. Their capabilities are not so big. They only allow you to view PSD files.