Exception Level 2 [1] They're analogous to "protection rings" on x86. Generally, EL0 is usermode, EL1 is kernel mode, EL2 is hypervisor, and EL3 is the "secure monitor"/firmware code, closest analogy I think would be SMM on x86. On top of all of that there's also trustzone with its own EL0 and EL1.

1: https://developer.arm.com/documentation/102412/0103/Privileg...