What is this drawing style called?

Question

It is a type of drawing widely used to create 3D models. shows layo's subject and is only drawn in pencil. But I don't know what this style is called because I would like to google some designs and then train with Blender. I leave you an image below to make you understand what I mean

Answer 1

It is a thumbnail. It is only preparatory work before making a 3D model.

Answer 2

What we used to call a rough, which is then cleaned up to produce finished artwork in whatever medium.