Thrust is caused by an engine or propeller, and it is the force that pushes the plane forward. Thrust is only needed to overcome drag, as drag is the force preventing the aircraft from moving in the first place. So in order for there to be flight, thrust must overcome drag, but when drag is more powerful than thrust, the plane slows down. And when it is greater than drag, it speeds up.
Thrust is a mechanical force, so to produce thrust the propulsion system in the engine must be in contact with a working fluid (T Benson,2014). Most of the time it is generated by the reaction of an accelerating mass of gas (T Benson,2014). The vector quantity has a magnitude and a direction