Velocity differs from speed in that it has a specific direction.
In physics, speed measures distance traveled over time, while velocity measures distance traveled over a specific vector over time—velocity can be interpreted as travel toward a goal. It therefore makes sense that this term is commonly used in discussing performance metrics on teams, especially scrum teams, as scrum suggests that sprints are supposed to tareget a specific goal rather than express an arbitrary collection of tasks. While there’s no authoritative definition of velocity for teams, this relationship implies that one version of scrum velocity would only count work done toward the goal and not other tasks (but this calls for a better description of what decisions this metric provides for; the analogy could simply not work when taken this far). Rather than optimize efficiency, teams must optimize toward their goals by seeking effectiveness.