The fundamental concepts, operating principles, and recent advancements in integrated sensing and communication (ISAC) are presented. A comprehensive review of multiband and large-frequency-ratio micro-wave/millimeter-wave transmission lines, antennas, and passive components—primarily filters and couplers—that are currently suitable for ISAC application scenarios is provided. Various implementation strategies and fabrication techniques for these multiband and high-frequency-ratio structures are comparatively analyzed. The technical characteristics, RF performance, and respective advantages and limitations of different design approaches are systematically summarized. This review offers a diverse and in-depth reference for the continued development of high-performance microwave/millimeter-wave front-end components tailored for ISAC applications.