on-screen reading

On-screen reading relates to reading type on the screen of a device, rather than in printed form.

Font rendering is handled by the operating system’s rasterizer. While Apple’s OS X does a great job of rendering all fine details of type on screen, the Windows rasterizer is less refined, so fonts in small sizes don’t look as good as in Mac OS.
The TrueType format was jointly developed by Apple and Microsoft in 1991, several years after the release of the PostScript Type 1 font format. Despite the format’s technical superiority (most of the system fonts on both Mac and Windows computers are TrueType) it never became popular amongst designers.