What is velocity?
Velocity can be defined as the rate of change of displacement. In other words,
velocity = displacement / time
In comparison, the speed is defined as the rate of change of distance. That is,
speed = distance traveled / time taken.
Unlike speed, which is a scalar quantity, velocity is a vector quantity. This means that velocity has both a magnitude and a direction. All the laws of vectors (such as vector addition, magnitude, etc.) are applicable for velocity as well.
The commonly used units of velocity are meter per second (m/s), miles per hour (miles/hr), kilometers per hour (km/hr), etc.
Often, people confuse speed and velocity. The difference lies in distance versus displacement. Speed relates to the distance traveled and cannot be zero for a moving object. Velocity, on the other hand, can be zero. Imagine the motion of a car in a perfect circle. For every completed round, the displacement is zero, while a finite distance has been traveled. Thus, the car has finite speed, but zero velocity (for every completed round).
Hope this helps.