https://en.wikipedia.org/wiki/ARM_architecture_family
A type or processor/CPU. The leading processor for mobile phones, and with this iteration, a real challenger to Intel for computers (because of the power/heat optimization).
In some ways, we are seeing or about to see another BetaMax vs VHS scenario. Intel is BetaMax, and ARM devices are VHS (because ARM can be licensed and made by other CPU manufacturers). This time, BetaMax/Intel will likely survive as having the dominant share at present, but ARM/VHS will likely compete well because of their advantages as well as having not built a very good system to run Intel based software on their processors. The current Intel debacle, with processors failing and needing replacement (and not being actively recalled) will only help ARM more.
I have not used an Apple PC since an Apple II in school, but I have and use one of the new ARM based machine daily. It could work to be my main, except my main is a dual screen ZenBook which is very handy.
At present, you will see these processors marketed in the Windows CoPilot+ machines, like the Surface Pro 11. Other machines will be available shortly, if not already available.