TrueType is the binary scalable font format originally created by Apple and nowadays is the most widely font format in the Mac and Microsoft Windows world.
A TrueType font file consists of a sequence of concatenated tables. The first of the tables is the font directory, a special table that facilitates access to the other tables in the font. The directory is followed by a sequence of tables containing the font data. These tables can appear in any order. Certain tables are required for all fonts. Others are optional depending upon the functionality expected of a particular font.
The required tables must appear in every valid TrueType font file. This is the list of the required tables:
cmap: character to glyph mapping
glyf: glyph data
head: font header
hhea: horizontal header
hmtx: horizontal metrics
loca: index to location
maxp: maximum profile
The complete TrueType font reference manual can be found at http://vrr.ucw.cz/doc/TTRefMan/index.html.