A file with an .ai extension is an Adobe Illustrator Artwork file that contains vector graphics on a single page. It uses points to create paths for displaying the image data, thus making it safe from losing image quality if it is enlarged. AI format finds its major usage for logos and print media. AI files can be opened with Adobe Illustrator, Adobe Acrobat DC, PaintShop Pro, and CorelDraw Graphics tools.
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 AI into many other file formats. Please see the complete list below.