Apple LaserWriter 12/640 PS - Manual (Page 368)

What is font substitution?
Font Substitution is an option in the Page Setup dialog box for certain
PostScript printers. When font substitution is turned on, these printers will
use their built-in equivalents for three bitmapped fonts (Times for New York,
Helvetica for Geneva, and Courier for Monaco).
What’s a downloadable font?
A downloadable font is a TrueType or PostScript font sent to some kinds of
printers, such as most PostScript Laser printers, by your system software. The
printer then uses the font to print your document.
If a printer has sufficient memory, it can hold more than one downloaded
font; otherwise, it must request the fonts it needs as necessary. This can be a
time-consuming process.
Some printers have hard disks attached to them for holding downloaded fonts.
A printer can get the fonts from its hard disk more quickly than it can
download them from the computer’s hard disk.
Your LaserWriter 12/640 PS printer can receive downloaded fonts.
343 Using Fonts With the Printer