How are they different ? Square have a right 90° angles while rhombus it doesn't have.But rhombus is more likely picture as a diamond shape because of its odd internal angular shape. they are the same because both square and rhombus are quadrilaterals and there sides are always equal.. hope it helps though its my own explanation
The difference of square to the rhombus:
Square -all interior angles are equAL, while
Rhombus- not all interior angles are equal.

The Similarity of square to the rhombus:
Square -has an equal sides while
Rhombus-has also an equal sides. 

That's why,Square is a rhombus  but Rhombus is not a square.

Hope this help.:)