I remember back in the day when people would “Jailbreak” iPhones, but never really picked up on what they were doing other than that it let them do stuff that those of us with “non-jailbroken” iPhones couldn’t do.
Are they just booting another OS, e.g. android? Also: why haven’t I heard of it in a while? Is it not possible on newer iPhones?
You rely on security exploits that grant access to low level stuff, which then allows for jailbreak. As security vulnerabilities get more and more discovered and fixed there’s just less opportunities to have root access.