4G is a mobile internet connection that operates at speeds between 100 Mbps and 1 Gbps over cellular networks or local Wi-Fi. It connects via a SIM card in a smartphone and allows internet access on the go but has coverage limitations. Fixed broadband is a high-speed home or office internet connection delivered via radio signals or fiber optic cables to a router, providing unlimited data through a consistent Wi-Fi network without usage caps but is stationary. The main differences between the two are that 4G is mobile but has coverage and speed restrictions while fixed broadband is stationary but offers faster, more reliable internet without usage limits.