Here's a breakdown:

* Positive Acceleration:

* Speeding up: The object is moving faster in the same direction.

* Example: A car accelerating from a stoplight.

* Negative Acceleration:

* Slowing down: The object is moving slower in the same direction.

* Example: A car braking to a stop.

* Changing direction: The object is moving in the opposite direction.

* Example: A ball thrown upwards slowing down as it reaches its peak.

Important Note: The concept of positive and negative acceleration depends on the chosen coordinate system. If you define the direction of motion as positive, then slowing down would be negative acceleration.