Wireless networking is one of the most emerging fields of today. These in the form of Wi-Fi have made a special place in the people homes, offices, etc. Wi-Fi is easy to deploy and is cheap but it is prone to many security related threats like active attacks such as modification of messages, denial of service, etc. and passive attacks such as traffic analysis, release of message contents, etc. This paper discusses Wi-Fi introduction, its working, characteristic, various 802.11 standards, and importance of security in Wi-Fi, security requirements in Wi-Fi and various security measures in Wi-Fi.