ClearType is MicrosoftCorporation's marketing term for their implementation of SubPixelAntiAliasing in MicrosoftWindows.

Useful, if not Linux-oriented information: you can activate ClearType support on your copy of MicrosoftWindows XP by going to Start menu -> Control Panel -> Display, clicking on the Apperance tab, and clicking on Effects.... Check the box next to Use the following method to smooth the edges of screen fonts and use the drop-down menu to select ClearType.

Looks best on LCD screens.