system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 how a jet engine works

I don't understand how jet engines work. It's awkward when I'm around people that are talking about jet engines - I just have to come up with an excuse to leave or just guess how they work.
Thanks for your help, webernet!
gpt
A gas turbine engine is a tube designed to take that air from the front (the intake), add fuel, burn it and the blow it out the back at a greater rate than it was sucked in, the result being called thrust.



In it's very simplest form it is a tube with 3 stages, with each stage performing a task, and each stage from front to back being part of a continuous stream of air that end up with it being ejected out the rear:


**Stage 1.**  Compressor - This is a fan, or set of fans, all stacked up together.  This is spun (we'll come back to what spins it later) and in doing so acts like a fan in your house, blowing the air in a certain direction, rearward.  Due to the fact that there are a number of fans all stacked up and acting in the same direction on the air, the force of these fans squashes the air up, compressing it many times over.  The air continues to move backward towards the next stage.

**Stage 2.**  Combustion Chamber - The compressed air is now passed onto a chamber where fuel is continuously being injected and ignited with spark plugs.  You might ask how the fire isn't put out by the fast moving air, the reason is that the way the air mixes and the ratio of fuel to air means that it's perfect conditions for combustion.  

In the process of being burned the air is suddenly charged with a huge amount of energy that is bursting to get out somewhere.  Because the fans at the front are still furiously pushing the air backwards, the air takes the path of least resistance into the 3rd stage.


**Stage 3.**  Turbine - This is very similar to the first stage, but whereas stage 1 (the compressor) is like a huge desk-fan, stage 3 (the turbine) acts like a windmill.  It is designed to be spun up by the hot expanding and high-energy air from the combustion chamber.  

Here's the clever part... Because the compressor and the turbine both sit in this tube at opposite ends, we connect the turbine (being spun by the hot air) to the compressor.  The hot air has so much energy it can spin up the turbine, in turn spinning up the compressor **and** still have enough energy to produce thrust out of the back.