A PSD, which stands for Photoshop Document, is a layered image file used in Adobe Photoshop.
To edit a PSD resource we recommend to use the industry standard program, which is Adobe Photoshop. However there are different software that you can use.
There are many tutorials and learning material that you can find about PSD edition on the Adobe website, that will give you access to a detailed information about the multiple features you can create when working with a PSD resource.