A typeface is a coordinated visual design for written forms. It can include related regular, bold and italic styles; a computer font supplies digital data implementing a particular selection or instance of that design. Thus choosing a typeface and choosing the file format used to store its glyphs are different decisions.
For a hypothetical family “Example Sans”, regular and bold styles can share a typographic family name while having different subfamily names. OpenType records this distinction in its naming table: name IDs 16 and 17 identify the typographic family and subfamily. Older family-name fields can group styles differently for application compatibility, so a filename alone is not a reliable account of the intended family.[ref]
Naming Table by Microsoft. Name IDs 1, 2, 16 and 17; extended typographic families and legacy four-style groupings
