What is in a name, Mac OS X, OS, etc.
Since Apple switched to the BSD based system based on NeXT OS from its bringing Steve Jobs on board, it has released OSes with the following naming on annual upgrades with a different name each year. The security patches which added a x.x.y y value were the common updates to those upgrades, generally available through Apple menu -> System Preferences or System Settings -> Software Update. Additional security updates are documented on this article:
Apple security releases - Apple Support
Here are the annual releases, which until 10.6 were only available on CD. Starting with 10.7, all annual releases were available on the App Store. Software updates, were also available through 10.15.7 on
OS X 10.0 through 10.0.4 Cheetah
OS X 10.1 through 10.1.5 Puma
OS X 10.2 through 10.2.8 Jaguar
OS X 10.3 through 10.3.9 Panther
OS X 10.4 through 10.4.11 Tiger. 10.4.4 and later versions were available for both PowerPC and Intel Macs. 10.4.11 was the last to support the Classic environment for virtualizing 9 applications.
OS X 10.5 through 10.5.8 Leopard. Leopard was the last dual boot operating system into Mac OS 9 and last to be able to boot PowerPC Macs.
OS X 10.6 through 10.6.8 Snow Leopard. 10.6.3 was the last retail release DVD. 10.6.6 the first to offer the App Store only for upgrading to 10.7. 10.6.8 offered an App Store that could upgrade to 10.11 El Capitan. 10.6.8 was the last operating system to support PowerPC OS X apps on Intel Macs. 10.6.4 was the first operating system to support ExFAT.
OS X 10.7 Lion through 10.7.5
OS X 10.8 Mountain Lion through 10.8.5
OS X 10.9 Maverics through 10.9.5
OS X 10.10 Yosemite through 10.10.5. 10.10.3 iPhoto replaced by Photos.
OS X 10.11 El Capitan through 10.11.6
Mac OS 10.12 Sierra through 10.12.6. 10.12.4 was the first supporting multifactor authentication.
Mac OS 10.13 High Sierra 10.13.6 The first operating system to support APFS, and all solid state drives formatted with, format APFS by default.
Mac OS 10.14 Mojave through 10.14.6 the last operating system to support 32 bit applications.
Mac OS 10.15 Catalina through 10.15.7 the first operating system to be all 64 bit. The last operating system operating system to have updates on Software downloads.
Mac OS 11.0 Big Sur through 11.7.8- currently being updated.
Mac OS 12.0 Monterey through 12.6.7- currently being updated
Mac OS 13.0 Ventura through 13.4.1- currently being updated.