General :: How Does Rooting Actually Work

I used to be a big IOS jailbreaker. I had been doing it for 4 years, before taking up android just a couple months ago. (and i must say, android is MUCH better). Anyway i know that basically during the jailbreaking process, the software uses an exploit on bootup and injects codes during the signature check on every level to make the idevice think that what it is running is legit, unmodified apple software. Hence why tethered jailbreaks need the original program to bypass iboot, because an exploit has not been found deep enough in the system to work in iboot aswell.

So how does rooting compare? Dont be afraid to explain using big words and in detail.