Most rhombuses do not have right angles, but a square is technically a rhombus and does have right angles at each of its corners. A rhombus is defined by having four sides of equal length, where opposite sides run parallel to each other, and opposite angles are equal. A square fulfills all these conditions.
There are many types of four-sided polygons, which are classified as quadrilaterals. This includes squares, rectangles, parallelograms, trapezoids and rhombuses. In some cases, a polygon can be more than one type of quadrilateral. A square fits the definition of both a rhombus and a rectangle. Furthermore, squares, rhombuses and rectangles are all parallelograms by definition.