3G refers to the third generation of wireless technology that allows for high-speed data services on mobile devices by complying with IMT-2000 standards, enabling uses beyond basic calling and SMS like GPS, mobile TV, and video calls, with typical download speeds around 3Mbps. While 3G remains popular, 4G provides improved speeds and latency and will eventually replace 3G as devices upgrade to the new 4G standard requiring different networking technology.