Here's why:

* Speed tells you how fast something is moving.

* Direction tells you which way it's moving.

Think of it like this:

* If you say a car is traveling at 60 miles per hour, you're describing its speed.

* If you say a car is traveling at 60 miles per hour eastbound, you're describing its velocity.

Velocity is a vector quantity, meaning it has both magnitude (speed) and direction.