Kerning is a specialized form of spacing between certain pairs of characters that look best when they overlap slightly, such as A and W (AW). Kerning dramatically improves the appearance of large text for headlines, but it often does not improve the appearance of text at small font sizes.
If the Kerning option is selected on the Property inspector's Text tab, Director kerns all the characters in the cast member according to standard kerning tables (for more information, see Setting text or field cast member properties). The setting you enter in the Kerning text box in the Text window or Font dialog box (for more information, see Formatting characters) supplements the standard kerning.