* Velocity is a measure of how fast something is moving and in what direction. If something is at rest, its velocity is zero.

* Acceleration is the rate of change of velocity. This means acceleration tells you how quickly the velocity is changing.

Here's a simple example:

Imagine a car stopped at a red light. Its velocity is zero. When the light turns green, the car starts moving. It accelerates forward.

* Initially, the car has zero velocity but is accelerating. The car is gaining speed, which means its velocity is increasing.

Other examples:

* A ball thrown straight up: At the very top of its trajectory, the ball momentarily stops before falling back down. At this peak, its velocity is zero, but it's still accelerating due to gravity.

* A car slowing down: Even as a car brakes to a stop, it's still accelerating. In this case, the acceleration is in the opposite direction of the car's motion (often called deceleration).

Key Point: Acceleration describes a change in velocity. Even if velocity is zero at a particular moment, acceleration can still be present if the velocity is about to change.