All shapes and sizes
A square has equal sides and every angle is a right angle (90°).
Also opposite sides are parallel.
A square also fits the definition of a rectangle (all angles are 90°), and a rhombus (all sides are equal length).
A trapezoid (called a trapezium in the UK) has a pair of opposite sides parallel.
It is called an Isosceles trapezoid if the sides that aren't parallel are equal in length and both angles coming from a parallel side are equal.
And a trapezium (UK: trapezoid) is a quadrilateral with NO parallel sides:
A rhombus is a four-sided shape where all sides have equal length.
Also opposite sides are parallel and opposite angles are equal.
Another interesting thing is that the diagonals meet in the middle at a right angle.
A rhombus is sometimes called a rhombus or a diamond.
It has two pairs of sides.
Each pair is made up of adjacent sides (they meet) that are equal in length.
The angles are equal where the pairs meet. Diagonals (dashed lines) meet at a right angle, and one of the diagonal bisects (cuts equally in half) the other.