Velocity is called a vector quantity because it has both magnitude and direction. A vector quantity is a physical quantity that requires both a numerical value (magnitude) and a specified direction to fully describe it.
In the case of velocity, the magnitude refers to the speed at which an object is moving, while the direction indicates the object's movement in a particular path. By considering both magnitude and direction, velocity provides a more complete description of motion than speed alone.
On the other hand, speed is a scalar quantity, which means it only has magnitude and does not have a specific direction associated with it. It represents the rate at which an object covers distance, irrespective of the direction of motion. In other words, speed tells you how fast an object is moving, but it does not convey any information about the object's direction.
To summarize, velocity includes both the speed and the direction of motion, making it a vector quantity, whereas speed represents only the magnitude of motion and is considered a scalar quantity.