Velocity is a measure of how much work (sum of the story points of done stories) a team can get done per iteration.
Velocity is helpful to predict how much work can be done in future iterations. Velocity changes and should be measured at the end of each iteration. It is worth noting that the velocity of teams cannot be compared as the sizing and estimation in each team varies from others.
Computing the initial velocity faces the “Cold start” issue, and can be done as follows: • based on historical data of previous similar projects, • running a few iterations and then calculate the velocity, • or based on expert judgment.