What is Orbit insertion?

Orbit insertion is the spaceflight operation of adjusting a spacecraft’s momentum, in particular to allow for entry into a stable orbit around a planet, moon, or other celestial body. This maneuver involves either deceleration from a speed in excess of the respective body’s escape velocity, or acceleration to it from a lower speed.

The result may also be a transfer orbit. There is e.g., the term descent orbit insertion. Often this is called orbit injection.