Here's why:

* Speed tells you how fast an object is moving, but not its direction. For example, a car traveling at 60 mph could be going north, south, east, or west.

* Velocity combines speed and direction. It tells you how fast an object is moving and in what direction. For example, a car traveling at 60 mph eastward has a velocity of 60 mph eastward.

Key points about velocity:

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

* It can be positive or negative depending on the direction of motion.

* It can change even if the speed remains constant. For example, a car turning a corner at a constant speed is changing its velocity because its direction is changing.