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.
Docx is well-known format for Microsoft Word documents. Introduced from 2007 with the release of Microsoft Office 2007, the structure of this new Document format was changed from plain binary to a combination of XML and binary files. Docx files can be opened with Word 2007 and lateral versions but not with the earlier versions of MS Word which support DOC file extensions.
You can also convert AI into many other file formats. Please see the complete list below.