Here's why:

* Velocity is a measure of both speed and direction.

* Acceleration is the rate at which velocity changes over time.

Examples of acceleration:

* A car speeding up.

* A car slowing down.

* A car turning a corner (changing direction).

* A ball thrown straight up in the air (changing direction and speed).

Important Notes:

* Acceleration can be positive or negative. Positive acceleration means velocity is increasing, while negative acceleration means velocity is decreasing (also known as deceleration).

* Acceleration can also be zero. This means the velocity is constant (not changing).