MacTeX is a redistribution of TeX Live, a typesetting environment. While TeX Live is designed to be cross-platform (running on Unix, macOS, and Windows), MacTeX includes Mac-specific utilities and front-ends. It is also pre-configured to work out-of-the-box with macOS as it provides sensible defaults for configuration options that, in TeX Live, are left up to the user to allow for its cross-platform compatibility. - Wikipedia See TeX Live.
TeX Live is a free software distribution for the TeX typesetting system that includes major TeX-related programs, macro packages, and fonts. It is the replacement of its no-longer supported counterpart teTeX. TeX Live is an easy way to get up and running with the TeX document production system. It provides a comprehensive TeX system with binaries for most flavors of Unix, including GNU/Linux, and also Windows. It includes all the major TeX-related programs, macro packages, and fonts that are free software, including support for many languages around the world.