This course/textbook provides a comprehensive introduction to the theoretical framework and practical applications of LED-based Visible Light Communications (VLC). Addressing the challenges of limited LED modulation bandwidth and complex indoor optical environments, it explores in-depth optical channel modeling, high-efficiency modulation formats (e.g., OFDM/DMT), and electrical-domain equalization techniques. The content covers the entire link analysis, from the transmitter (driver circuits and optical design) to the receiver (high-sensitivity photodetection and signal demodulation), extending to cutting-edge applications such as MIMO parallel transmission, underwater VLC, and high-precision indoor positioning. This study aims to build a multi-disciplinary knowledge base to solve spectrum scarcity and high-density access issues in future wireless networks.