Technical
Hohmann Transfer
A fuel-efficient two-burn manoeuvre that moves a spacecraft between two circular orbits via an intermediate elliptical transfer orbit.
A Hohmann transfer is the classic minimum-energy way to change between two coplanar circular orbits. A first burn raises (or lowers) the orbit into an ellipse tangent to both, and a second burn at the opposite apsis circularises it at the target altitude.
It is a foundational concept in mission and manoeuvre planning, and the delta-v of each burn drives propellant budgets and, ultimately, mission lifetime.