Surface plasmons are like waves that happen on the surface of really small things, like nano-sized particles. Just like how waves happen in water, surface plasmons happen on a really tiny scale.
When light shines on these particles, it can make the tiny particles shake and create these waves. These waves are called surface plasmons.
Scientists can use these waves to study these tiny particles and learn more about them. They can also use these waves to make really cool things like sensors that can detect tiny amounts of things, like bacteria or chemicals.
So basically, surface plasmons are tiny waves that happen on the surface of really small things like nano-sized particles, and scientists can use them to learn about and make really cool things.