A rhombus is one of several types of four-sided shapes known as quadrilaterals. Other quadrilaterals are rectangles, parallelograms, kites and trapezoids. In addition to the square, a rhombus is similar to a parallelogram because both shapes have two sets of parallel sides. While all rhombuses are parallelograms, a parallelogram is not a rhombus because it does not have four equal sides. The area of a rhombus can be calculated by multiplying its height by its side length. The perimeter is calculated by multiplying the length of a side by four.