Here's why:

* Speed tells you how fast something is moving.

* Direction tells you which way it's moving.

Velocity combines these two pieces of information. It's a vector quantity, meaning it has both magnitude (speed) and direction.

Example:

* Two cars could be traveling at the same speed of 60 mph.

* If one car is traveling north and the other is traveling east, they have different velocities even though they have the same speed.

In summary: Velocity is a more complete description of motion than speed alone because it considers both how fast and in what direction an object is moving.