Technical illustration is rather a broad label, covering everything from architectural blueprints, to product design, to concept design for things like robots and armor. Traditionally technical artists relied on rulers and 'rapidograph' pens to get smooth, exact lines with even weight and concise proportions, often showing the lines through the 'skin' of the object so inner workings can be seen. This drawing is how Sorrek's hut (from the last post) is built.
Examples of some tecnical illustrations include everything from the Thomas Jefferson's Architectural designs to the batmobile, and these designs for Tron, to product detailing such as this one.
Illustrator is a funny beast, but I think I'm starting to get the hang of it.