macOS - Wikipedia
https://en.wikipedia.org/wiki/MacOS
macOS (/ˌmækoʊˈɛs/; previously Mac OS X and later OS X) is a series of proprietary graphical operating systems developed and marketed by Apple Inc. since 2001.
Mac OS X & macOS names - Macworld UK
https://www.macworld.co.uk/feature/os-x-macos-versions-3662757/
Every version of Mac OS X and macOS ever from the first to the latest macOS, plus how to tell which version you have. Curious about the versions of Mac OS X that came before?
Downloads - Download macOS
https://www.downloadmacos.com/
macOS Catalina gives you more of everything you love about Mac. Experience music, TV, and podcasts in three all-new Mac apps. Enjoy your favorite iPad apps now on your Mac.
List of Mac OS versions | Apple Wiki | Fandom
https://apple.fandom.com/wiki/List_of_Mac_OS_versions
Note: The headings on this list indicate the Macintosh System bundle names; the bullet points indicate the version of the System File included in that bundle. This is to make it clearer for people searching for specific bundle versions as opposed to System File versions. Finder File versions are not indicated.
Mac Support
https://macosx.com/
Mac OS X System & Mac Software. All questions and problems related to running OS X should be posted here as well as those for miscellaneous software not more specifically covered in other forums.
MacOS Archives - The Mac Go -World of Mac
https://themacgo.com/category/macos/
macOS Catalina 10.15.7 for mac dmg free download full version. Complete setup macOS Catalina 10.15.7 (19H2) offline installer for mac OS with direct link.