PostScript fonts are based on the Adobe PostScript language. There are many font formats. Type 1 fonts, one of the PostScript formats, are widely used in desktop publishing although OpenType is fast becoming the standard.
Type 1 fonts use a subset of the PostScript language. PostScript Type 1 font files consist of two files — a screen font with bitmap information for on-screen display and a file with outline information for printing the font. For commercial printing, both of the Type 1 font files must be included with the application file.
Due to differences in their structure, Mac and Windows PostScript Type 1 fonts are not cross-platform compatible.