is in many respects, a subtle art form requiring as much patience, skill and practice as oil painting
, playing a harp
, or tap dancing on a tightrope.
The actual term kerning is quite out-dated, as it is derived from technology which has fallen out of use (for the most part). On a letterpress, each character was designed on a block, or slug, with a little extra space around it, so that the letter would not contact the sides of other letters. Some characters had portions that extended off of the metal block onto a circular portion of the slug called a kern. Extra space could be added to pull the characters further apart, and this process is called tracking. Tracking condenses and expands many characters simultaneously, whereas kerning operates on the relationships between two characters at a time. Another similar process is leading (pronounced like the element plus an "ing", not like the act of directing), which is the vertical spacing of lines of text. As with tracking, leading is something that alters large chunks of text at a time. All these terms are still used today in computer-aided typography, yet are tied to the days of Johann Gutenberg. Digital typographic endeavors are not only infinitely easier to kern, but allow for a greater range of distances between characters. Overlapping, for instance, would be nearly impossible with a letterpress (you would have to print over the same sheet multiple times, or create custom slugs of overlapped characters...both of these would be expensive and difficult).
Kerning is in essence a way to unify the spaces between characters in a word, in order to give the word greater clarity and readability.