macOS installation
How do I upgrade my MacBook Air with the latest macOS?
The latest goes by macOS12, Monterey. Depending on the specifications
of your present Mac, an unknown; as hardware may be outdated by now.
There is a myth, in these 'system upgrades' are now known as Updates.
Much more has changed in two versions after Catalina; nothing simple.
You could look through the older systems; and see Monterey, there too:
• How to get old versions of macOS - Apple Support
https://support.apple.com/en-us/HT211683
"Learn how to upgrade to macOS Monterey, the latest version of macOS."
Which macOS does your Mac presently have living inside? How old?
Some fairly recent have balked, when confronted by Monterey os12.
Good luck & happy trails! ☃️❄️