The jet engine is a reaction engine discharging a fast-moving jet that generates thrust by jet propulsion (application of Newton’s third law).
According to this law, for every action, there is an equal and opposite reaction. The statement means that in every interaction, there is a pair of forces acting on the two interacting objects. The size of the forces on the first object equals the size of the force on the second object and are opposite in the direction.
Considering the jet engine, simply put, the air enters the engine from the front with the help of the spinning turbine. Within the engine, this air is condensed and ignites with the use of fuel. Then, the hot exhaust gases come out forcefully from the rear of the engine and thus the airplane moves forward.