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 MHT extension represent a web page archive format that can be created by a number of different applications. The format is known as archive format because it saves the web HTML code and associated resources in a single file. These resources include anything linked to the webpage such as images, applets, animations, audio files and so on.
You can also convert AI into many other file formats. Please see the complete list below.