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).