This document discusses properties of parallelograms and related shapes. It defines a parallelogram as a quadrilateral with both pairs of opposite sides parallel. The key properties are: 1) Both pairs of opposite sides are congruent 2) Both pairs of opposite angles are congruent 3) Consecutive angles are supplementary 4) The diagonals of a parallelogram bisect each other It then discusses specific types of parallelograms including rectangles, rhombi, and squares, noting additional properties they possess.