Basically a software engineer gets software to work.
Software engineers design and develop computer software. A typical software engineer will analyse end users' needs and from these will design, construct, deploy, and maintain software applications. He may design the application and allow a programmer to develop it, he may develop algorithms. He may produce the program code himself.
For more information on software engineering, see the US Bureau of Labour Statistics on www.bls.gov/oco/ocos303.htm or Wikipedia on http://en.wikipedia.org/wiki/Software_engineering.