HP PCL/PJL reference (PCL 5 Printer Language) - Technical Reference Manual Part I

7-4 Fonts EN
Spacing
Another characteristic that differentiates fonts is spacing. Fonts have
either fixed or proportional spacing. Fixed-spaced fonts (Figure 7-3)
are those in which the inter-character spacing is constant.
Proportionally-spaced fonts (Figure 7-4) are those in which the
inter-character spacing varies with the natural shape of a character.
Figure 7-3 Fixed Spacing
Figure 7-4 Proportional Spacing