The Microsoft Download Center IEEE 802.11 Wireless LAN Security with Microsoft Windows XP pagew contains the following overview:

Although wireless LAN networks provide freedom of movement, they also require you to address security issues that are not as prevalent on a private cabling system for a wired LAN technology such as Ethernet. The main security issues are the authentication of wireless clients and the encryption and data integrity of wireless LAN frames. This article discusses the security issues of IEEE 802.11 wireless networks and shows how the Microsoft Windows XP operating system can be used to make 802.11 wireless networks as secure as the current set of 802.11-related technologies allow.