A drawing that shows a real object with accurate sizes reduced or enlarged by a certain amount (called the scale).
The scale is shown as the length in the drawing, then a colon (":"), then the matching length on the real thing.
Example: this drawing has a scale of "1:10", so anything drawn with the size of "1" would have a size of "10" in the real world, so a measurement of 150mm on the drawing would be 1500mm on the real horse.