The paper reviews the Fermi gas model of one-dimensional conductors, focusing on exact solutions for specific coupling constants in the single-chain problem (Tomonaga model and Luther-Emery model). Renormalization group arguments are used to extend these solutions to arbitrary coupling values. The behavior of response functions is studied to investigate possible ground states and instabilities. The relationship between the Fermi gas model and other models is discussed, providing further insights into the system's behavior. The model is generalized to a set of coupled chains to describe quasi-one-dimensional systems, and the crossover from one-dimensional to three-dimensional behavior and the type of ordering are examined. The paper also covers the perturbational treatment of the model, the renormalization group treatment, and the scaling aspects of the renormalization group.The paper reviews the Fermi gas model of one-dimensional conductors, focusing on exact solutions for specific coupling constants in the single-chain problem (Tomonaga model and Luther-Emery model). Renormalization group arguments are used to extend these solutions to arbitrary coupling values. The behavior of response functions is studied to investigate possible ground states and instabilities. The relationship between the Fermi gas model and other models is discussed, providing further insights into the system's behavior. The model is generalized to a set of coupled chains to describe quasi-one-dimensional systems, and the crossover from one-dimensional to three-dimensional behavior and the type of ordering are examined. The paper also covers the perturbational treatment of the model, the renormalization group treatment, and the scaling aspects of the renormalization group.