TrueType is a rival format to PostScript which was adopted by both Microsoft and Apple, although it only really caught on with Windows users.
A Type rasterizer is built into both Macintosh and Windows operating systems.
TrueType fonts are held in a single file which can contain variants such as regular, italic, bold, and bold italic.
From Mac OS 8.5 onwards, Macs can use the same TrueType file format as PCs, with the extension ‘.ttf’ or ’.ttc’. However, Macs also have their own TrueType fomat, ‘.dfont’, which is not compatible with Window.