That is a rhombus, an equal sided parallelogram. It is diamond-shaped.
Its a diamond :]
A rhombus
A rhombus.
The rectangle
a Rhombus...
A rhombus.
A shape that has four right angles is a rectangle. If all four sides are equal in length, then it is a square.
The shape you're describing is a rhombus. A rhombus has four sides of equal length, but its angles are not constrained to be right angles, meaning they can be acute or obtuse. This characteristic distinguishes it from a square, which has both equal side lengths and right angles.
rectangle
square
octagon
This is a parallelogram called a rectangle. A square has four right angles and four sides that are equal in length.