Okay kiddo, imagine you're looking at a big hill from far away. The top of the hill is flat like a table, but the sides of the hill slope down steeply. Now, imagine a line drawn all the way around the hill where the flat top ends and the steep sides begin. That line is called the caprock escarpment.
The caprock escarpment is made up of a really hard rock layer that protects the softer rocks underneath from eroding away. This hard rock is usually made of something called limestone or sandstone. It forms a sort of wall that runs along the edge of the hill.
People also call the caprock escarpment the "break of the plains" because it's where the flat land suddenly drops off into steep slopes leading to lower elevations.
So, caprock escarpment is like a big wall that runs along the edge of a hill that's made of really strong rock, and it's called "break of the plains".