In Raman Spectroscopy the Raman effect is utilised to detect the fingerprint of a molecule. By exposing molecules to specific light, the molecules starts to vibrate and emit a spectrum of light. This light is then measured revealing the identity of the molecules.
With Surface Enhanced Raman Spectography a molecule can be attached to a surface and emmited light can be enhanced. Using a nano structured metal surface the interaction between molecules and light can be enhanced up to a factor 1.000.000.000 (or more in special cases).