The Ready universe describes motion through physics. Physics is the study of how energy and matter work together to create our physical universe. For example, a basic idea in physics is that the distance you travel over a specific amount of time is your velocity.
If you're walking, you can travel one mile in about 20 minutes. So in one hour you'll travel three miles. That's "three miles an hour". In Ready, we measure velocity in "meters per second" or "m/s"/ So an object can be set to move across the screen at "1 m/s".