Question

What is parellelogram? and What is rhombus?

Answer 1

A parallelogram is a quadrilateral with each pair of opposite sides are parallel.
Rhombus is a parallelogram wit sides of equal length

Answer 2

a parallelogram is basically a quadrilateral 
whose   digonals bisect each other and opposite sides are parallel and equal

in rhombuses the diogonals bisect each other at 90 and adjacent sides are =