Instantaneous speed is measured at a specific point in time. It's not an average over a period of time, but rather the speed at that exact moment.

Here's a way to think about it:

* Average speed: Imagine driving 100 miles in 2 hours. Your average speed would be 50 mph (100 miles / 2 hours).

* Instantaneous speed: Now imagine looking at your speedometer at a particular moment during that drive. The number you see on the speedometer is your instantaneous speed at that precise instant.

Think of it like taking a snapshot of your speed rather than looking at a video of your entire journey.