Plasmons are collective oscillations of free electrons in a material, typically found in metals. When light interacts with these electrons, it can cause them to move in a synchronized manner, creating waves known as plasmons. This phenomenon is essential in fields like nanotechnology and plasmonics, where it can enhance light-matter interactions. There are two main types of plasmons: bulk plasmons, which occur throughout the material, and surface plasmons, which are confined to the surface of a metal. Surface plasmons are particularly useful in applications such as sensors and imaging techniques, as they can amplify signals at the nanoscale.