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I recently began using PostScript fonts in Windows with AmiPro as my word processor. These fonts came with printed cards indicating the glyph mappings; I could look at the card and it would tell me that a specific character lived in cell 246, and if I entered Alt-0246 at the numeric keypad that glyph would appear on the screen. If I loaded the font into Fontographer for Windows, these glyphs would be arrayed in cells according to the map provided by Adobe with the fonts. Fontographer also revealed that these fonts had other, "unmapped" glyphs assigned to cells above 255.
Given what appeared to be a hard correspondence among what I saw in Fontographer, what was printed in Adobe's maps, and what was displayed when I entered something at the keyboard, I naively assumed that PostScript fonts were operating much like my bitmapped fonts under DOS. There were some obvious differences, the primary one being that glyphs of different sizes were all drawn from the same font resource files under PostScript, but it appeared as if a glyph lived in a certain cell.