Abstract: With the fast development of nanoscience and nanotechnology, research on the unique optical properties of metal nanostructures and related applications has rapidly grown into an important branch discipline of nano-optics, known as plasmonics, with abundant content and extensive applications in many fields such as biology, chemistry, renewable energy, and information technology. This article introduces some basic concepts of surface plasmons, including localized surface plasmons and propagating surface plasmon polaritons. An overview of various important applications in bio/chemo sensing, nanolasers, ultrafast optical switches, surface plasmon-based logic, and so forth is presented.