how does a lightbulb function?

Question: how does a lightbulb function?
- Keywords:
  electric,
  electricity,
  light,
  lightbulb
Asked by kizzy786 to Philip on 11 Jun 2011.
- Philip Denniff answered on 11 Jun 2011:
  
  The old non energy efficient light bulbs work by electricity flowing through a resistance wire and heating it up until it glows white hot. The hot metal gives off light. No idea how energy efficient bulbs work

Question: how does a lightbulb function?