There is only one file type that uses the .TTC extension:
TrueType Font Collection
Collection of fonts saved in the TrueType (.TTF) format; used to deliver multiple fonts in a single file; useful for combining fonts that share many glyphs in common.
TTC files allow multiple fonts to share glyph sets, which reduces the overall disk space required by the fonts. TrueType Font Collections are most often used for East Asian languages, such as Japanese and Korean.
Updated: September 22, 2010