Beginners know how to draw squares, circles and rectangles.
Pros know how to draw boxes, spheres and cylinders.

"Wait, what's the difference?", you ask.

Simple: the former are flat 2d shapes, while the latter are 3d objects (also known as primitive forms or primitives) that are affected by perspective.

While this might sound mundane or even easy, getting good at drawing primitives has the potential of bringing your art to the next level.