The document provides an overview of augmented sixth chords, including their structure, types (Italian, French, German), and resolution. It explains that they are built from an augmented sixth interval, with additional thirds and fifths depending on the type. The Italian sixth adds a third above the bass, the French sixth adds a third and fourth, and the German sixth adds a third and perfect fifth. All resolve outward to scale degree 5, with some variations depending on the type.