Here's a breakdown:

* Velocity: Speed in a given direction.

* Acceleration: The change in velocity over time.

Key points about acceleration:

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

* Positive acceleration means velocity is increasing.

* Negative acceleration means velocity is decreasing (often called deceleration).

* Zero acceleration means the velocity is constant (not changing).

Example:

A car speeding up from 0 to 60 mph in 5 seconds has a positive acceleration. A car slowing down from 60 mph to 0 mph has a negative acceleration. A car traveling at a constant 60 mph has zero acceleration.