Wi-Fi is a wireless networking technology that uses radio waves to provide wireless internet access to devices within a 150-300 foot range. It was invented in the 1990s in Australia by Dr. John O'Sullivan. A Wi-Fi network uses a router connected to a modem to connect to the internet and broadcast a radio signal to nearby devices, allowing them wireless access to browse and use the internet without wires. Wi-Fi provides advantages over wired connections like mobility and easy installation. However, it also has limitations like a smaller range and potential security risks compared to wired networks.