Wi-Fi was invented by the committee of IEEE 802.11 in 1997 and its main techniques came from John O’Sullivan and his team from Cydney university in Australia, who solved the critical problem about signal interference. The idea of Wi-Fi first came from a company called NCR in the 1980s. This company wanted to address the problem of connection of cash register without wired network. Eventually, they successfully invented Wave LAN, which is recognized as a pioneer of Wi-Fi. Next, when it comes to usages, internet access is a significant section. People can use it on a laptop, personal computer, smartphone, and tablet. Additionally, it could be divided into two aspects, which is also important. One is city-wide and the other one is campus-wide. In conclusion, Wi-Fi is rather useful because people can visit the Internet without using wires of the network and it is becoming cheaper and cheaper. However, it is limited by its range. In addition, network security is still not safe currently.