A rhombus is a four-sided shape with all sides equal in length and opposite sides parallel. The diagonals intersect at right angles and bisect each other. A parallelogram is also a four-sided shape with opposite sides parallel, but its opposite sides do not necessarily have to be equal in length. The diagonals of a parallelogram bisect each other, but they do not necessarily intersect at right angles.
In summary, a rhombus has all sides equal in length and the diagonals intersect at right angles, whereas a parallelogram has opposite sides parallel but not necessarily equal in length and the diagonals bisect each other but not necessarily intersect at right angles.