This document provides an overview of different defensive coverages that a quarterback may see and how to read them pre-snap using the acronym "BOX D.E.A." which stands for the number of players in the box, the depth and alignment of defensive backs, and where the defensive backs are looking. It describes 6 main coverages - man, man free, two deep zone, three deep zone, four deep quarter zone, and two deep man under. The document emphasizes that pre-snap reads may change post-snap and to watch safety rotations for coverage adjustments.