How does a jet's throttle actually work?
The throttle (or thrust lever) in a gas turbine engine adjusts the thrust produced by controlling the fuel flow to the combustion chamber. 

Most of the modern engines are actually controlled by the Full Authority Digital Engine (or electronics) Control, FADEC (or Engine Control unit)- so the signals from the throttle are sent to the computer, which regulates the fuel flow based on various parameters (including engine safety) thereby adjusting thrust. The computer handles the additional components of the engines like the thrust reversers and afterburners.

The image below shows the throttle controlling the fuel system through the engine control in the Pratt &amp; Whitney F100 engine that powers F-15 and F-16.



Image from kaskus.co.id