Properties of Parallelogram
If a quadrilateral has a pair of parallel opposite sides, then it’s a special polygon called Parallelogram. The properties of a parallelogram are as follows:

The opposite sides are parallel and congruent
The opposite angles are congruent
The consecutive angles are supplementary
If any one of the angles is a right angle, then all the other angles will be at right angle
The two diagonals bisect each other
Each diagonal bisects the parallelogram into two congruent triangles
The Sum of square of all the sides of parallelogram is equal to the sum of square of its diagonals. It is also called parallelogram law