SpyBot-S&D searches your hard drive for so-called spy- or adbots; little modules that are responsible for the ads many programs display. But many of these modules also transmit information about your surfing behaviour and more to the net.
If SpyBot-S&D finds such modules, it can remove them – or replace them with empty dummies in case their host software won’t run with its bot removed. In most cases, the host still runs fine after removing the bot.
For a list of ‘supported’ bots see the feature lists below. The Spybot-S&D interface is so easy, that updates just require replacing a file of about 80k in size. Those updates are distributed by my software mailinglist, at the authors page and are also available from inside the programs update section.