Answer:
A scale drawing is a drawing that shows the size of an object reduced or enlarged by a certain amount. The most common example is a map.
If we were to create a real size map of a house it would be a HUGE map. We wouldn't be able to grab it using our hands, and it wouldn't be useful either. The idea of a map is to have a diagrammatic representation of something.
Intead, we create maps where the size of the house is reduced by a certain scale. So we can see the distribution of the house, and -at the same time- know the measures of it.
I am attaching an example of a map. It's the map of mexico, and you can see the scale of the map at the bottom.