Yesterday I was asked by an employee in a non-technical department "What do application engineers do?" [for a solder company] Expecting a horribly technical answer, I offered this analogy instead:
Our job is like baking a cake.
1) We put together the materials exactly as the directions instruct.
2) The materials are heated in an oven.
3) We try out the finished product.
4) If there is a problem with the end product, we check the materials, the way we put them together, and how it was heated. After any issues are fixed, the next one should be perfect.