TrueType refers to an outline font standard first developed by Apple Computer, and later embraced by Microsoft, as a competitor to Adobe Systems, Inc.'s PostScript. Glyphs in TrueType fonts are made of quadratic Bezier curves.
The standard includes a virtual machine that executes programs inside the font that "hint" the glyphs (that is, modify them slightly so that the outline rasterizer produces fewer artifacts). The FreeType project (http://www.freetype.org/) ran into legal problems when trying to create an independent implementation of the TrueType standard, which made no mention of the patents on the hinting VM. More recent FreeType releases include an automatic hinter that analyzes glyph shapes and corrects them.