Here's why:

* Velocity is a measure of how fast an object is moving and in what direction.

* Acceleration describes how the velocity of an object changes over time.

Think of it this way:

* If you're driving a car at a constant speed, your velocity is constant, and your acceleration is zero.

* If you step on the gas pedal, you increase your speed, meaning your velocity is changing. This change in velocity over time is acceleration.

* If you slam on the brakes, you decrease your speed (or even change direction), which also means your velocity is changing. This is also acceleration, although it's often referred to as deceleration.