This document discusses parallel lines and angles formed when lines are cut by a transversal. It begins by defining parallel lines and explaining that a transversal is a line that intersects two or more lines at different points. It then defines and provides examples of several types of angles formed, including alternate interior/exterior angles, same side interior/exterior angles, and corresponding angles. Groups are then assigned to prove properties of these angles for parallel lines cut by a transversal. The document concludes with practice problems finding missing angle measures using the properties and an assignment involving parallel lines cut by a transversal.