The fundamental modulation methods used in 5G/5G-Advanced are Pi/2 BPSK, QPSK, 16-QAM, 64-QAM, 256-QAM, and 1024-QAM. Those used in Wi-Fi 6/7 are BPSK, QPSK, 16-QAM, 64-QAM, 256-QAM, 1024-QAM, and 4096-QAM. That used in Bluetooth 5/6 is GFSK. These are the methods, therefore, that we are going to briefly review in this chapter. For all but GFSK, the modulation is such that the modulated carrier is linearly related to the baseband signal, i.e., the data carrying signal at or near zero frequency. Such modulation is referred to as linear modulation. For GFSK, the modulated carrier is non-linearly related to the baseband signal thus the modulation is referred to as non-linear modulation. In this chapter, we first review the fundamentals of baseband transmission techniques, as these form the foundation upon which the techniques involving the modulation of an RF carrier are based. We then take a high-level view of the relevant linearly modulated methods followed by one of GFSK.