Delta-V is a term used in space travel to describe the change in velocity needed for a spacecraft to perform maneuvers, such as launching, orbiting, or landing. It is a crucial concept in astrodynamics, as it helps engineers calculate the amount of fuel required for a mission and the spacecraft's trajectory. In simple terms, Delta-V measures how much speed a spacecraft must gain or lose to achieve its goals. For example, to escape Earth's gravity, a spacecraft needs a specific Delta-V to reach orbit, while landing on another celestial body also requires precise calculations of Delta-V to ensure a safe touchdown.