Here's why:

* Speed is a measure of how fast something is moving. It's typically calculated as distance traveled over a period of time.

* Instantaneous speed refers to the speed of an object at a specific moment in time, or at a specific point in its trajectory.

For example, if a car is traveling at 60 mph, that's its average speed. But if we want to know how fast the car is going at the exact moment it passes a certain mile marker, that's its instantaneous speed.