In typography, kerning is the process of altering the space between specific pairs of letters in a proportional font. The goal of kerning is to improve the overall balance of space between letters.
A simple proportional font will simply specify the right and left sidebearings, or boundries, of each letter. However, depending on the adjacent letter, the space may be reduced (and occasionally increased) to improve the appearance of the letters. For example, "A" and "V" can be placed closer together so that the top left of the "V" is directly above the bottom right of the "A".
Kerning is implicitly part of digital type design, and advanced typographic systems allow the specification of kerning. It is commonly confused with tracking, but these are two separate concepts.