Question

Is a rhombus a square

Answer 1

A rhombus is a quadrilateral in which all of the sides have equal length. 
A rhombus can be a square sometimes if the angles are 90°. 

 

Answer 2

Sometimes, but not every time.

A rhombus can be a square, but it doesn't always have to be.

A square is a rhombus that has special, extra requirements ...
its angles must be 90°.  So every square is a rhombus, but
not every rhombus is a square.