DGN files are drawings created by and supported by CAD applications such as MicroStation and Intergraph Interactive Graphics Design System. It is used for creating and saving designs for construction projects such as highways, bridges, and buildings. The format is similar to Autodesk’s DWG file format and is considered its competitor.
PSD, Photoshop Document, represents Adobe Photoshop's native file format used for graphics designing and development. PSD files may include image layers, adjustment layers, layer masks, annotations, file information, keywords, and other Photoshop-specific elements. Photoshop files have default extension as PSD and have a maximum height and width of 30,000 pixels, and a length limit of two gigabytes.
You can also convert DGN into many other file formats. Please see the complete list below.