This paper provides a comprehensive review of the theory and experimental tests for cosmic ray (CR) propagation in the Milky Way up to energies of $10^{15}$ eV. The authors discuss the basic principles of CR propagation, including the role of magnetic fields, interstellar medium (ISM), and plasma effects. They describe various techniques for computing observational consequences, such as analytical and numerical methods, and compare these with data from direct and indirect observations, particularly gamma-ray telescopes. The paper also covers specific topics like electron and antiparticle behavior, and highlights recent advances in isotopic composition and element spectra measurements. The authors emphasize the importance of CRs as a direct probe of the ISM and their influence on star formation and other astrophysical processes. They conclude by discussing the challenges and future directions in CR propagation research, including the need for more sophisticated models and the integration of CR data with other astrophysical observations.This paper provides a comprehensive review of the theory and experimental tests for cosmic ray (CR) propagation in the Milky Way up to energies of $10^{15}$ eV. The authors discuss the basic principles of CR propagation, including the role of magnetic fields, interstellar medium (ISM), and plasma effects. They describe various techniques for computing observational consequences, such as analytical and numerical methods, and compare these with data from direct and indirect observations, particularly gamma-ray telescopes. The paper also covers specific topics like electron and antiparticle behavior, and highlights recent advances in isotopic composition and element spectra measurements. The authors emphasize the importance of CRs as a direct probe of the ISM and their influence on star formation and other astrophysical processes. They conclude by discussing the challenges and future directions in CR propagation research, including the need for more sophisticated models and the integration of CR data with other astrophysical observations.