Li Fi uses visible light communication technology to transmit data wirelessly using light. It provides higher bandwidth than Wi Fi and can be used in environments where Wi Fi is not available or restricted. Li Fi works by varying the intensity of light from LED bulbs to transmit digital signals and uses photodiodes to receive the signals. It has applications in airways, hospitals, and underwater communications and provides advantages like green IT and use of existing lighting infrastructure for internet access. However, it requires line of sight and does not work in dark or outdoor environments unlike Wi Fi.