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.
Files with .DOC extension represent documents generated by Microsoft Word or other word processing documents in binary file format. The extension was initially used for plain text documentation on several different operating systems. It can contain several different type of data such as images, formatted as well as plain text, graphs, charts, embedded objects, links, pages, page formatting, print settings and a lot others.
You can also convert AI into many other file formats. Please see the complete list below.