From blessing Classic Mac OS, through SUM and the first Recovery partition in Mac OS X Lion, right up to 1 True Recovery on Apple silicon Macs.
frOS
How your M1 Mac starts up in the Recovery mode of your choice, or when it decides you need to take a trip to Recovery to fix an issue.
There’s 1 True Recovery, Fallback Recovery and one other recovery mode. Disambiguation, explanation and how this changed in macOS 11.4.
The Eclectic Light Company 