Explain IT to the business

As a software architect, and especially during periods of stress you might find yourself in a position where you have to explain a technical detail to an involved business party. They won't help you program but they might need to be reassured why we decided to invest time (and therefore money) in something they can't grasp. I often found this more difficult than previously imagined so I decided to share some explanations. First off is "Threading". If you're a business fellow and you're still riddled or an architect and you find something wrong or too far fetched please let me know, I'm sure we'll align business and IT after all :)