A quadrilateral is a four-sided polygon that can take many shapes. The sides can be straight or curved, but in most cases, they are straight. Common types of quadrilaterals include squares, rectangles, trapezoids, and parallelograms. Each type has its own unique properties, such as equal sides or angles. The sum of the interior angles in any quadrilateral is always 360 degrees. This means that if you know three angles, you can easily find the fourth one by subtracting the sum of the known angles from 360. Quadrilaterals are everywhere in our daily lives, from windows to tables!