1. Change in speed: Velocity is a vector quantity, meaning it has both magnitude (speed) and direction. If the speed of an object increases or decreases, its velocity changes.

2. Change in direction: Even if the speed remains constant, a change in the direction of motion will result in a change in velocity. For example, a car traveling in a circle at a constant speed is still changing velocity because its direction is constantly changing.

3. Change in both speed and direction: This is the most common scenario. A car accelerating while turning is changing both its speed and direction, resulting in a change in its velocity.

Let me know if you'd like a more in-depth explanation of any of these!