The article reviews the emerging field of graphene plasmonics, which combines the unique properties of graphene with the principles of plasmonics. Graphene, a two-dimensional (2D) material, exhibits intrinsic plasmons that are tunable, adjustable, and have low dissipation. The combination of graphene with noble-metal nanostructures offers exciting applications in conventional plasmonics. The versatility of graphene allows for the development of novel optical devices operating across different frequency ranges, from terahertz to visible light, with advantages such as high speed, low driving voltage, low power consumption, and a small physical footprint. The optical properties of graphene are discussed in detail, including its linear dispersion relation, chiral symmetry, and strong optical non-linearity. The article also explores the impact of doping, gating, and strain on the optical properties of graphene. Additionally, it covers the optical properties of other 2D materials, such as bilayer and trilayer graphene, and their potential for applications in telecommunications and valleytronics. The article further delves into the theory of 2D plasmons, including the plasmon dispersion relation, plasmarons, and plasmon-electron interactions. It highlights the potential of graphene-based plasmonics for enhancing light-matter interactions and developing active plasmonics, such as photodetectors and optical modulators. The combination of graphene with conventional plasmonic nanostructures and metamaterials is explored, emphasizing the potential for ultrasensitive chemical and biosensors, non-linear optical elements, and efficient photodetectors. Overall, the article underscores the potential of graphene plasmonics to revolutionize optoelectronics and optical computing, offering new opportunities for fundamental physics research and practical applications.The article reviews the emerging field of graphene plasmonics, which combines the unique properties of graphene with the principles of plasmonics. Graphene, a two-dimensional (2D) material, exhibits intrinsic plasmons that are tunable, adjustable, and have low dissipation. The combination of graphene with noble-metal nanostructures offers exciting applications in conventional plasmonics. The versatility of graphene allows for the development of novel optical devices operating across different frequency ranges, from terahertz to visible light, with advantages such as high speed, low driving voltage, low power consumption, and a small physical footprint. The optical properties of graphene are discussed in detail, including its linear dispersion relation, chiral symmetry, and strong optical non-linearity. The article also explores the impact of doping, gating, and strain on the optical properties of graphene. Additionally, it covers the optical properties of other 2D materials, such as bilayer and trilayer graphene, and their potential for applications in telecommunications and valleytronics. The article further delves into the theory of 2D plasmons, including the plasmon dispersion relation, plasmarons, and plasmon-electron interactions. It highlights the potential of graphene-based plasmonics for enhancing light-matter interactions and developing active plasmonics, such as photodetectors and optical modulators. The combination of graphene with conventional plasmonic nanostructures and metamaterials is explored, emphasizing the potential for ultrasensitive chemical and biosensors, non-linear optical elements, and efficient photodetectors. Overall, the article underscores the potential of graphene plasmonics to revolutionize optoelectronics and optical computing, offering new opportunities for fundamental physics research and practical applications.