Suitcase
The suitcase format for TrueType is used on Mac OS. It adds additional Apple-specific information.
Like TTC, it can handle multiple fonts within a single file. But unlike TTC, those fonts need not be within the same family.
Suitcases come in resource-fork and data-fork formats. The resource-fork version was the original suitcase format. Data-fork-only suitcases, which place the resource fork contents into the data fork, were first supported in Mac OS X. A suitcase packed into the data-fork-only format has the extension dfont.
Read more about this topic: TrueType, Technical Notes, File Formats