### Instruction: What is a jet engine?
### Response: A jet engine is a reaction engine used for propulsion, most commonly in airplanes. It works by compressing and discharging heated gas, and follows Newton's third law of motion. Most jet engine used in airplanes are breathing axial flow gas turbines. These gas turbines are powered using aviation turbine fuel (avtur) or more commonly called jet fuel. The gas turbines have at least three stages: a compressor, a combustor, and a turbine.