Kerning is a term in typography that refers to the spacing between two individual characters. It reduces the optical space between two letters by allowing parts of letters to overlap vertically. Kerning enhances readability by making text appear more natural.
Without kerning, each letter would take up a solid block of space as if it were within an invisible rectangle. However, some letter shapes have angled or horizontal strokes that leave extra space in their top or bottom corners. For example, if an A and a V are placed next to each other without kerning, they will appear as if a space is between them. Kerning allows them to vertically overlap and fit together, taking up less space and appearing more natural.
Digital fonts include a kerning table that defines the proper spacing between every possible letter combination, allowing software to automatically apply kerning where necessary. Word processors and desktop publishing software allow you to override those values and manually adjust kerning. Good kerning also changes with font size — smaller font sizes need more space between letters to remain legible, letting you kern text more tightly at larger sizes.
NOTE: Kerning should not be confused with tracking. Kerning adjusts the spacing between individual pairs of letters, while tracking applies to an entire block of text.