web beacons / action tags?

In the Microsoft privacy statement
(http://www.microsoft.com/info/privacy.htm) is the following text:

Q: Does the site track my visit on Microsoft.com?
A:To ensure we are publishing content customers need and want,
microsoft.com collects aggregated site-visitation statistics using
cookies. When someone visits the site, a cookie is placed on the
customer�s machine (if the customer accepts cookies) or is read if the
customer has visited the site previously. Clear gif technology, also
known as a web beacon or action tag, assists in delivering the cookie.
This technology tells us how many visitors clicked on key elements
(such as links or graphics) on a microsoft.com Web page. We aggregate
all usage information, which means we do not track individuals' use of
the site. We never share tracking information outside of Microsoft,
and do not allow other companies to place clear gifs on our sites.

I know about using clear (transparent) GIFs for page layout, but I've
never heard of "clear GIF technology" or "web beacons" or "action
tags".

Anyone?

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