Here's a breakdown:

* Acceleration is the rate of change of velocity.

* Velocity has both speed and direction.

* Negative acceleration means the velocity is decreasing in the direction of the object's current motion.

Examples:

* A car braking to a stop: The car is moving forward (positive velocity) but the brakes are causing it to slow down (negative acceleration).

* A ball thrown upwards: As the ball travels upwards, gravity acts on it, causing it to slow down until it momentarily stops at its highest point (negative acceleration).

* An object sliding to a stop on a rough surface: The friction between the object and the surface causes it to slow down (negative acceleration).

Important Note: Negative acceleration doesn't always mean the object is moving backwards. It simply means the object is slowing down in its current direction of motion.