1. Type 1 and Type 3 fonts
Type 1 and Type 3 fonts were developed by Adobe for professional digital typesetting. Using PostScript, the glyphs are outline fonts described with cubic Bezier curves. Type 1 fonts were restricted to a subset of the PostScript language, and used Adobe’s hinting system, which used to be very expensive. Type 3 allowed unrestricted use of the PostScript language, but didn’t include any hint information, which could lead to visible rendering artifacts on low-resolution devices (such as computer screens and dot-matrix printers).
2. TrueType font
TrueType is a font system originally developed by Apple, Inc. It was intended to replace Type 1 fonts, which many felt were too expensive. Unlike Type 1 fonts, TrueType glyphs are described with quadratic Bezier curves. It is currently very popular and implementations exist for all major operating systems.
3. OpenType font
OpenType is a smartfont system designed by Adobe and Microsoft. OpenType fonts contain outlines in either the TrueType or Type 1 (actually CFF) format together with a wide range of metadata.
METAFONT uses a different sort of glyph description. Like TrueType, it is a vector font description system. It draws glyphs using strokes produced by moving a polygonal or elliptical pen approximated by a polygon along a path made from cubic Bézier splines and straight line segments, or by filling such paths. Although when stroking a path the envelope of the stroke is never actually generated, the method causes no loss of accuracy or resolution.