Actually it's called "kernel streaming". It's a very nice technique for sending sound directly to the soundcard, thus bypassing Windows's "kmixer" process. Bypassing kmixer is always considered a good thing because apparently kmixer can mangle the bits of a digital audio stream before it gets passed to the soundcard. I've heard kmixer might possibly do extremely stupid things including but not limited to upsampling 44.1kHz cd audio to 48kHz, and the back down to 44.1kHz before sending it to the soundcard, which results in a loss of data.
Foobar2000 is a fantastic music player that has several nice plugins, one of which does kernel streaming. Aside from that plugin, I love foobar 2000 for its no-nonsense minimalist interface and of course for the way it sounds.
Winamp with the ASIO plugin is the only non-kernel streaming method I've heard of for bypassing kmixer, but I don't like winamp and I think kernel streaming works with a larger set of soundcards. I deleted winamp once I got foobar2000. One more thing - I know kmixer is a problem with Windows2000 systems, but it may not be an issue with Windows XP. I just don't know since I use 2000.
Mike U.