> I always assumed afterburners just meant opening the throttle up but there must be more to it
No, as the name implies it's literally pouring in fuel after the turbine, in the exhaust. The exhaust is hot, yes, but cooler than the combustion chambers (which reside in between the turbine and compressor). So if you have some special fuel that's very hard to ignite then maybe you need some help to get the afterburning started.
I always assumed afterburners just meant opening the throttle up but there must be more to it