How to Interpret Velocity vs. Time Graphs?

[lkj6778]

My physics lab is using a Motion Detector, to measure the time it takes for a high frequency pulse to travel from the detector to an object and back.

I have several questions about Velocity vs Time:

What does a horizontal line (with 0 velocity) mean? Does that mean to walk backwards, walk forwards, run, etc?

What does a horizontal line (with 0.5 velocity) mean? Does that mean to walk backwards, walk forwards, run, etc?

What does a horizontal line (with -0.5 velocity) mean? Does that mean to walk backwards, walk forwards, run, etc?

What does a vertical line pointing straight up mean? Quickly run backwards right?

What does a vertical line pointing straight down mean? Quickly run forward right?

 

[mfb]

0 velocity means no motion.
What positive and negative means depends on your setup.

What does a vertical line pointing straight up mean? Quickly run backwards right?

It is a velocity versus time plot. So which quantity makes a fast change? How is that usually called?