Microsoft Knowledge Base Article 815485 contains the following summary:
This article discusses the new Wi-Fi Protected Access (WPA)
update in Microsoft Windows XP.
The Institute of Electrical & Electronics Engineers (IEEE) 802.11i wireless networking standard specifies improvements to wireless local area networking (LAN) security. The 802.11i standard is currently in draft form, with ratification due at the end of 2003. The 802.11i standard addresses many of the security issues of the original 802.11 standard. While the new IEEE 802.11i standard is being ratified, wireless vendors have agreed on an interoperable interim standard known as Wi-Fi Protected Access (WPA).