A PSD file is a layered image file used in Adobe Photoshop. PSD, which stands for Photoshop Document, is the default format that Photoshop uses for saving data. PSD is a proprietary file that allows the user to work with the images’ individual layers even after the file has been saved. Smart Objects are layers that contain image data from raster or vector images. Smart Objects preserve an image’s source content with all its original characteristics, enabling you to perform nondestructive editing to the layer. In the case of mockups you can edit the contents of a smart objects. When you edit a Smart Object, the source content is opened in other Photoshop file. When you save changes to the source content, the edits appear in the initial Photoshop document.