What is the difference between invention and designing?

Invention is something one finds that did not exist before. Someone invented the airplane. Someone else invented the light bulb. Yet someone else invented the telephone. Designing is not something that is unique to invention. Designing usually means a blueprint or map or methodology to instantiate an idea around which you can put your arms around be it an invention, a discovery, or even an existing design (re-design). The idea behind a design is to make the best uses of resources available to produce a product or idea.