Velocity is called a vector quantity because it has both magnitude and direction associated with it. A vector quantity is a measurement that requires both of these components to fully describe it. In the case of velocity, the magnitude represents the speed of an object, while the direction indicates the object's movement.
On the other hand, speed is a scalar quantity. Scalar quantities only have magnitude and do not have a specific direction associated with them. When discussing the motion of an object, speed refers to the magnitude of the velocity without regard to its direction.
To illustrate the difference between velocity and speed, consider the example of a car moving on a straight road. If we say the car is traveling at 60 kilometers per hour, that's the speed of the car. However, if we specify that the car is moving east at 60 kilometers per hour, we are describing its velocity, taking into account both the magnitude (60 km/h) and the direction (east).
In summary, velocity includes both magnitude and direction, making it a vector quantity, while speed refers to the magnitude of velocity and is a scalar quantity.