From the Latin ingeniare, to design.
Engineers use principles of science to design structures, machines, and products of all kinds.
They look for better ways to use existing resources and often develop new materials. Engineers have had a direct role in the creation of most of modern technology - the tools, materials, techniques, and power sources that make our lives easier. Consider the shower in your house. The faucets are valves, which were designed by an engineer. The water comes through piping from a central water supply.