Typography is the art, process, or style of setting type and creating glyphs.

In traditional typography, text is composed to create a readable, coherent, and visually satisfying whole that works invisibly, without the awareness of the reader. Even distribution of typeset material, with a minimum of distractions and anomalies, is aimed at producing clarity and transparency.

Display typography is a potent element in graphic design, where there is less concern for readability and more potential for using type in an artistic manner. Type is combined with negative space, graphic elements and pictures, forming relationships and dialog between words and images.

Wikipedia: http://en.wikipedia.org/wiki/Typography