TrueType is the scalable font technology built into Windows. TrueType font files (.TTF) are made up of a number of tables, some mandatory (such as the 'glyph' table containing glyph outlines), others optional (like the 'kern' table). TrueType was designed this way to make the format extensible.
If you use TrueType fonts, Newlook uses the same font to display text on the screen and to print. (The screen fonts provide a very close approximation of printed characters.) TrueType font names are preceded by in the Font box on the Appearance setting window. Newlook mono, the default monospaced font, is automatically installed when you set up Newlook.