One character, one horizontal slot
In a monospace font, each character advances the same fixed distance before the next one begins. The narrow strokes of an “i” do not make its slot smaller, and the broad shape of a “W” does not make it larger. A type designer can center or otherwise position each shape within that shared slot, but the spacing between character positions stays consistent.
That fixed rhythm makes text behave like a grid. If several lines contain characters in the same positions, those characters line up vertically—even when one line has a skinny letter where another has a wide one.
Why the grid is useful
The benefit becomes obvious in code, command-line screens, and plain-text tables. A column of numbers can stay aligned without a layout system calculating the width of every word. In programming, indentation and spacing are visible parts of the structure, so a stable character grid makes it easier to scan blocks of text and spot differences between lines.
Proportional fonts, where letters have different widths, use space more economically and often feel more natural for paragraphs. Monospace fonts accept the opposite tradeoff: some characters leave more empty space around their shapes, but the positions remain predictable. The font turns text into a simple grid, so alignment can survive even when the display has no richer formatting.
