simsun.ttc

TrueType Collection Reference

A .ttc file is a TrueType Collection. The file packs several TrueType fonts into one container. The fonts share common glyph data, which decreases the file size. East Asian system fonts on Windows, for example MS Gothic and Meiryo, ship as collections. Operating systems load the members as separate fonts.

A file extension is only a part of the file name. It does not give a guarantee about the format or the content of a file. But on Windows, the extension selects the program that opens the file.