Li-Fi uses visible light communication to transmit data. Basically flickering a light on and off based on a specific pattern to transmit a message.
The big benefit of Li-Fi is its speed which is much faster then Wi-Fi permits. Estonian scientists were able to achieve 224 gigabits per second speeds in a lab environment. Another potential benefit is security. Because light is constricted to a specific area and doesn't pass through objects such as walls, someone from outside can't easily get onto the network.