High-entropy materials (HEMs) constitute an innovative category of advanced materials distinguished by their distinctive atomic arrangements and remarkable multifunctional attributes. This thorough overview critically analyzes the core principles, synthesis methods, and novel applications of HEMs, emphasizing their transformative potentials in electromagnetic and biological fields. This study examines how the high configurational entropy effect, lattice distortion, and slow diffusion mechanisms facilitate the stabilization of single-phase systems including numerous primary elements. Recent advancements in HEM development have demonstrated exceptional skills in electromagnetic wave absorption, attaining reflection losses of up to - 35.10 dB via nano-domain designs and synergistic dielectric-magnetic loss mechanisms. Including rare-earth elements has substantially affected magnetic ordering and transition temperatures, with La-based compounds displaying spontaneous magnetization of approximately 15.2 emu/g. In biomedical applications, innovative HEM formulations have attained improved biocompatibility with a diminished Young's modulus (69-140 GPa) and exceptional corrosion resistance. This review provides a detailed roadmap for researchers and engineers focused on the practical application of advanced materials, through a methodical analysis of current developments in energy storage, catalysis, electromagnetic shielding, and biological applications. We emphasize the significance of composition design and processing parameters in attaining customized features for specific technological applications while recognizing key difficulties and future research avenues in this swiftly advancing sector.