Plain English Meaning
The speed that gets you to a higher altitude the fastest in terms of minutes on the clock. Fly at VY when your goal is to reach a desired altitude as quickly as possible.
Full Definition
The airspeed that produces the greatest gain in altitude per unit of time for a given aircraft configuration and weight. At VY, the difference between power available and power required is at its maximum, allowing the aircraft to climb to a target altitude in the shortest time.
Context Anchor
You see VY in the airplane’s handbook, takeoff and climb performance information, and climb .