Squares and rectangles are the most common quadrilaterals. They have four right angles and parallel sides. Rectangles have two pairs of parallel sides. Squares have two pairs of parallel sides as well, but it also has 4 equal sides, which a rectangle doesn't have.A rectangle has two pairs of congruent sides.
The other figures(parallelograms, rhombuses, and kites)are not that popular, but they are very easy to spot, but you might just not notice them.