Here's a breakdown:

* Velocity: Velocity is a measure of both speed and direction. It tells us how fast an object is moving and in what direction.

* Acceleration: Acceleration is the rate of change of velocity. It means that the velocity of an object is changing over time.

Acceleration can be caused by:

* A change in speed: If an object speeds up or slows down, its velocity changes.

* A change in direction: Even if an object maintains a constant speed, a change in direction means its velocity changes.

* A combination of both: An object can accelerate by changing both its speed and direction.

Examples:

* A car accelerating from rest to 60 mph is experiencing a change in velocity because its speed is increasing.

* A car turning a corner at a constant speed is also experiencing a change in velocity because its direction is changing.

* A ball thrown upwards experiences a change in velocity as it slows down due to gravity and then changes direction to fall back down.

Key point: Acceleration is the cause of a change in velocity. Without acceleration, an object's velocity will remain constant.