the two polygons are congruent if they are the same shape with the same measurements. If they can be flipped, rotated, and/or slid to look identical then they're congruent.

Not all polygons are regular by definition. An irregular polygon may have non-congruent sides or non congruent angles or both. A regular polygon will always have both congruent sides and angles.

They are said to be regular polygons such as equilateral triangles, squares and other polygons that have congruent sides and equal congruent interior angles.