Here's why:

* Velocity is a vector quantity: It has both magnitude (speed) and direction.

* Velocity-time graphs plot velocity on the y-axis and time on the x-axis. This allows you to see how velocity changes over time.

* The slope of the line on a velocity-time graph represents acceleration. Acceleration is the rate of change of velocity.

* The area under the curve of a velocity-time graph represents displacement. Displacement is the overall change in position.

Other graphs where you might see velocity-related information:

* Position-time graph: You can *derive* velocity from the slope of a position-time graph (velocity is the rate of change of position).

* Acceleration-time graph: You can *calculate* velocity by finding the area under the curve of an acceleration-time graph (velocity is the integral of acceleration).