"Psychedelica" — type specimen
A monospaced font, also called a fixed-pitch, fixed-width, or a non-proportional font, is a font whose letters and their characters each occupy the complete same amount of their horizontal space.
This contrasts with variable of the width fonts, where the letters differ in size from one another, as do the same spacings in between many letters. The two high use letters 'I' and 'E' in both cases simply do not need the same footprint, while both differ in center to next letter edge (and center to center) spacing distance needs (margins) in variable width fonts. These variables that change are the offset from what would otherwise be monospaced centering. In a modern proportional font every dimension can be scaled and changed, but such sizing mathematically must still maintain the monospacing or variable spacing.
— Type design
Letterstudio, KABK www.letterstudio.org