Shot noise in mesoscopic conductors is a phenomenon arising from the quantization of charge and provides information about the system that cannot be obtained through conductance measurements. It is more sensitive to electron-electron interactions than average conductance. The review discusses shot noise in various systems, including tunnel barriers, quantum point contacts, resonant tunnel barriers, metallic diffusive wires, chaotic cavities, and edge channels in the quantum Hall effect. It also covers hybrid normal-superconducting structures and noise in strongly correlated systems. The review presents a scattering approach, classical Langevin and Boltzmann-Langevin methods, and discusses results from these approaches. It highlights the importance of shot noise in understanding mesoscopic systems, including the role of thermal fluctuations, partition noise, and the effects of interactions. The review also addresses unsolved problems and future directions in the field.Shot noise in mesoscopic conductors is a phenomenon arising from the quantization of charge and provides information about the system that cannot be obtained through conductance measurements. It is more sensitive to electron-electron interactions than average conductance. The review discusses shot noise in various systems, including tunnel barriers, quantum point contacts, resonant tunnel barriers, metallic diffusive wires, chaotic cavities, and edge channels in the quantum Hall effect. It also covers hybrid normal-superconducting structures and noise in strongly correlated systems. The review presents a scattering approach, classical Langevin and Boltzmann-Langevin methods, and discusses results from these approaches. It highlights the importance of shot noise in understanding mesoscopic systems, including the role of thermal fluctuations, partition noise, and the effects of interactions. The review also addresses unsolved problems and future directions in the field.