Light Fidelity (Li-Fi) is a complementary technology to the typical technologies based on Radio Frequency (RF). Unlike RF, Li-Fi's operating range is in the visible light spectrum. Therefore, Li-Fi has advantages over RF technologies such as higher bandwidth, zero electromagnetic interference, and a high transmission rate. However, constant technological innovation in the area of Li-Fi-based systems leads us to study the most current transmission and reception techniques for this technology. In this paper, state-of-the-art multiplexing, modulation, and demodulation techniques applied to Li-Fi technology are presented and analyzed. For this purpose, the most relevant technical parameters involved in these techniques are described. Finally, after an exhaustive review of techniques, we present the Free Space Optical-Orthogonal Frequency Multiple Access (FSO-OFDM) and Free Space Optical Code Division Multiple Access (FSO-CDMA) techniques and their applications in Li-Fi systems.