Kerning- In typography, setting characters tightly together so that parts of the letter shapes interlock.
Leading (Lead/Line Spacing)- Originally, the thin strips of lead inserted between lines of hot metal type to provide space between lines. The term now refers to the space between printed lines of type whether actual lead (hot type) is used or not (as in photo composition) Leading is specified in points.
Tracking (Letter Spacing)- Space placed between letters in typography to "open up" the letters visually. In phototypesetting, the space between letters is not limited by metal and the conventional or "normal" space may be increased or reduced for special purposes.
