Here's a breakdown:

* Velocity: This is how fast an object is moving and in what direction.

* Change in velocity: This means how much the velocity of an object has changed, either in speed or direction, or both.

* Time interval: This is the duration of the period over which the velocity changes.

Think of it like this:

Imagine a car speeding up on a highway. To calculate the average acceleration, we would:

1. Measure the car's initial velocity.

2. Measure the car's final velocity.

3. Calculate the difference between the initial and final velocities (the change in velocity).

4. Divide the change in velocity by the time it took to change.

The formula for average acceleration is:

Average Acceleration = (Final Velocity - Initial Velocity) / Time

Key points about average acceleration:

* It's a vector quantity, meaning it has both magnitude (how much) and direction.

* It doesn't tell you the acceleration at any specific point in time, but rather the overall acceleration over a period.

* It can be positive, negative, or zero. Positive means the object is speeding up, negative means it's slowing down, and zero means it's moving at a constant velocity.

Example:

A car starts from rest (initial velocity = 0 m/s) and reaches a velocity of 20 m/s in 5 seconds.

* Change in velocity: 20 m/s - 0 m/s = 20 m/s

* Average acceleration: 20 m/s / 5 s = 4 m/s²

Therefore, the car's average acceleration is 4 meters per second squared.