So,
A rhombus is a quadrilateral with four equal sides. This means that all four sides are of equal lengths. So each side is the same length. A rhombus's vertices do not have to be any particular angle.
A square is a special case. It is both a rectangle and a rhombus because it has four right angles (rectangle) and four equal sides (rhombus).
So is a rhombus sometimes a square? Yes, when its angles equal 90°. No, when its angles do not equal 90°. So a rhombus can SOMETIMES be a square.