technical illustration
We've all been there. You have a point to make, and it would just be easier to sketch it out. Where are the cocktail napkins?
Sometimes the only way to get someone to understand what you're saying is to show a picture. When it comes to technical concepts, diagrams transfer 10X the information in 1 tenth the time, and the word count doesn't hit 1000.
Help manuals, training materials, repair guides; they all benefit from the use of clear images. Whether it be a line drawing, a conceptual diagram, or a photographic quality 3d render, the audience will "get it" much more quickly.