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ELI5: What part of a jet engine actually generates the thrust?

Hello, I've recently been reading up on jet engines and how they work. Air gets sucked in, compressed, injected into the combustion chamber to create expanding gas (that's how I understand it) so what part is actually generating the thrust, the turbine spinning or the gas being forced out of the back? And while I'm here, can anyone explain how the afterburner works? I understand it reheats the gas but how does that generate more thrust? Thanks!
gpt
The gases being forced out the back are the source of thrust.  It's actually different depending on what type of jet engines you're talking about.  

Turbojet engines (all of the early jets, plus most older fighter jets) are all about the hot gases coming out from the turbines to provide thrust. 

Turbofan engines (think airliners) on the other hand, actually generate the vast majority of their thrust from the cool air being blown back by the giant fan blades at the very front of the engine.  A small part of the air gets sucked into the core of the engine, where it's compressed and burned to run the turbines, which in turn drive all the other components.  This exhaust does provide some thrust as well.  But most of the air (80% or more) bypasses the core entirely, providing thrust from the fan alone.

As for the turbines spinning?  Jet engines are actually powered in reverse, sort of.  The first 2/3 of the engine exists mostly to feed the rear 1/3 of the engine, and in turn the rear third actually provides the power to run the front third.  That's all the turbines are there for, but it's the part that makes it all work.

Afterburners are a pretty simple concept, actually.  They work by dumping huge amounts of raw jet fuel straight into the superheated exhaust gases, where they instantly ignite and provide even more thrust in the form of those awesome blazing exhaust flames.  Basically, they turn the jet exhaust into a rocket engine of sorts.  It consumes horrific amounts of fuel, but the sheer burst of power is worth it when a fighter really needs every last shred of power it can get.