The chapter provides an overview of surface-enhanced Raman spectroscopy (SERS) and related plasmonic effects. It begins with a preface that outlines the notations, units, and conventions used throughout the book. The first section offers a quick overview of SERS, covering its basic principles, probes, substrates, and other important aspects such as enhancements, sample preparation, and signal characteristics. It also discusses related techniques and applications, including improved sensitivity, comparisons with fluorescence spectroscopy, and specific SERS applications. The chapter then delves into the history and current status of SERS, highlighting recent advancements and hot topics in the field. It provides a general outline of the book's content, emphasizing its "spirit" and different reading plans. The section on Raman spectroscopy and related optical techniques introduces the discovery of the Raman effect, its applications, instrumentation, and the energy levels of molecules. It also covers optical absorption, emission, scattering, and the concept of cross-sections. The chapter continues with a detailed exploration of plasmons and plasmonics, explaining the optical properties of noble metals, the definition and history of plasmons, and the electromagnetic modes of planar interfaces and localized surface plasmon polaritons (LSPPs). It discusses the coupling of PSPP modes with light, local field enhancements, and the interaction of SPPs. The section on SERS enhancement factors and related topics covers the definition and experimental measurement of these factors, the main electromagnetic effects in SERS, and the chemical enhancement mechanisms. It also includes a formal derivation of SERS electromagnetic enhancements and discusses surface-enhanced fluorescence (SEF). The chapter then addresses the calculation of electromagnetic enhancements, both analytically and numerically, and provides examples and discussions on EM enhancements and plasmon resonances. It explores the effects of shape, gap effects, and other factors on EM enhancements. The section on metallic colloids and other SERS substrates discusses the properties and characterization of colloidal solutions, the stability of colloidal solutions, and the application of SERS with metallic colloids. It also covers the 'chloride activation' of SERS signals and signal fluctuations. Recent developments in SERS, including single-molecule SERS, tip-enhanced Raman spectroscopy (TERS), new substrates from nanotechnology, and optical forces, are covered. The chapter concludes with a discussion on applications of SERS, including analyte engineering, substrate reproducibility, and commercialization. Finally, the chapter includes appendices on density functional theory (DFT) calculations for Raman spectroscopy, Maxwell's equations in media, the Lorentz model of atomic/molecular polarizability, the dielectric function of gold and silver, plane waves and planar interfaces, ellipsoids in the electrostatic approximation, and Mie theory and its implementation.The chapter provides an overview of surface-enhanced Raman spectroscopy (SERS) and related plasmonic effects. It begins with a preface that outlines the notations, units, and conventions used throughout the book. The first section offers a quick overview of SERS, covering its basic principles, probes, substrates, and other important aspects such as enhancements, sample preparation, and signal characteristics. It also discusses related techniques and applications, including improved sensitivity, comparisons with fluorescence spectroscopy, and specific SERS applications. The chapter then delves into the history and current status of SERS, highlighting recent advancements and hot topics in the field. It provides a general outline of the book's content, emphasizing its "spirit" and different reading plans. The section on Raman spectroscopy and related optical techniques introduces the discovery of the Raman effect, its applications, instrumentation, and the energy levels of molecules. It also covers optical absorption, emission, scattering, and the concept of cross-sections. The chapter continues with a detailed exploration of plasmons and plasmonics, explaining the optical properties of noble metals, the definition and history of plasmons, and the electromagnetic modes of planar interfaces and localized surface plasmon polaritons (LSPPs). It discusses the coupling of PSPP modes with light, local field enhancements, and the interaction of SPPs. The section on SERS enhancement factors and related topics covers the definition and experimental measurement of these factors, the main electromagnetic effects in SERS, and the chemical enhancement mechanisms. It also includes a formal derivation of SERS electromagnetic enhancements and discusses surface-enhanced fluorescence (SEF). The chapter then addresses the calculation of electromagnetic enhancements, both analytically and numerically, and provides examples and discussions on EM enhancements and plasmon resonances. It explores the effects of shape, gap effects, and other factors on EM enhancements. The section on metallic colloids and other SERS substrates discusses the properties and characterization of colloidal solutions, the stability of colloidal solutions, and the application of SERS with metallic colloids. It also covers the 'chloride activation' of SERS signals and signal fluctuations. Recent developments in SERS, including single-molecule SERS, tip-enhanced Raman spectroscopy (TERS), new substrates from nanotechnology, and optical forces, are covered. The chapter concludes with a discussion on applications of SERS, including analyte engineering, substrate reproducibility, and commercialization. Finally, the chapter includes appendices on density functional theory (DFT) calculations for Raman spectroscopy, Maxwell's equations in media, the Lorentz model of atomic/molecular polarizability, the dielectric function of gold and silver, plane waves and planar interfaces, ellipsoids in the electrostatic approximation, and Mie theory and its implementation.