Cosmic rays represent one of the most compelling phenomena in high‑energy astrophysics, originating from both Galactic and extragalactic environments and spanning energies from mega‑electron volts to beyond electron volts. This review synthesizes current knowledge on their composition, sources, spectral features, and detection techniques. Galactic Cosmic Rays are primarily accelerated in supernova remnants and superbubbles, while extragalactic contributions are linked to active galactic nuclei and gamma‑ray bursts. The cosmic ray spectrum exhibits distinct structures, including the knee at  eV and the ankle at   eV, marking the transition between Galactic and extragalactic origins. Recent direct detection experiments (AMS‑02, DAMPE, CALET) have revealed additional spectral features such as hardening near 500 GeV and softening around 10 TeV, challenging the traditional single power‑law description. Ground‑based observatories (Pierre Auger, LHAASO, HAWC) complement these findings by probing ultra‑high‑energy regimes and providing evidence for anisotropies in arrival directions. The results emphasize that cosmic ray behavior reflects a complex interplay of acceleration mechanisms, propagation effects, and source diversity. Conclusions highlight the necessity of integrating space‑based and ground‑based observations to reduce uncertainties in energy calibration and composition, particularly in the transition region between the knee and the ankle. This combined approach is essential for advancing our understanding of cosmic ray origins and their role in shaping high‑energy astrophysical processes.