A .mac may refer to any of the following:
Originally known as iTools, .Mac is a group of online services from Apple computers. .Mac gives Apple macOS users a place to host their web page, e-mail, store files, make greeting cards, and utilize a website review service. On June 09, 2008, Apple announced .Mac would be converted to MobileMe.
The .mac is a file extension for MacPaint files.
Apple terms, MobileMe, Online service