Isometric drawing is way of presenting designs/drawings in three dimensions. In order for a design to appear three dimensional, often a 30 degree angle is applied to its sides.
It’s often used in technical drawings as it does not require the need for a classic perspective where lines converge into a dot towards the horizon. The great advantage of using isometric design is that allows for a libary of easy to assemble building blocks that can be composed into a very clear drawing that allows users to zoom in at multiple levels.
It can give rise to great illustrations as below:
These type of illustrations are recommended for technical drawings originating from Thermaflex as to create a unique instantly recognizable style.
The grid to use is a 3:2 grid, as below