CoolType is a software technology, introduced by Adobe Systems in 2000, to increase the legibility of text on color LCDs like laptop or TFT monitors, especially to make reading long text, like E-Books, easier. Although it is primarily for LCDs, the legibility on CRT monitors is also improved.
As with ClearType, Quartz and FreeType, CoolType uses subpixel rendering to effectively triple the usual horizontal resolution of the screen. This makes the text sharper, but the colors might be slightly incorrect at the edges. However, the human eye is better at detecting variations in intensity than in color, and these discrepancies are not usually noticeable.