* Acceleration is the rate of change of velocity. This means it describes how quickly the object's speed or direction is changing.

* Zero acceleration indicates that the velocity is not changing.

Examples:

* A car traveling at a constant speed in a straight line: It has zero acceleration even though it's moving.

* A ball thrown upwards at the peak of its trajectory: At the peak, its velocity momentarily becomes zero, and it has zero acceleration before it starts falling back down.

In simpler terms:

Think of it like this: If you're walking at a steady pace, you're moving, but you're not accelerating. Your speed isn't changing.