5G is the fifth-generation cellular network technology, succeeding 4G, and is defined by the 3GPP's Release 15 specifications and the ITU's IMT-2020 framework. The first large-scale commercial deployment occurred on April 3, 2019, when South Korea launched its national network, followed shortly by Verizon in the U.S., and it operates by dividing areas into cells served by base stations using low-, mid-, or high-band spectrum. Compared to 4G, 5G aims for peak data rates of 20 Gbit/s downlink and 10 Gbit/s uplink, ultra-low latency, and massive connection density, enabling applications like enhanced mobile broadband, fixed wireless access, private industrial networks, and network slicing. Early research traces back to 2008 with NASA and M2Mi, and gained momentum in 2012 with the founding of NYU Wireless and the University of Surrey's 5G Innovation Centre, followed by trials from Samsung, NTT Docomo, and Huawei. The rollout has raised concerns about deployment costs, energy consumption, vendor security, and unsubstantiated health claims, while 5G is expected to coexist with 4G for many years.