A parallelogram is a four-sided object that has parallel opposite sides. A square is a parallelogram. If you take the square and tilt it to one side, it’s still a parallelogram as long as its lines remain parallel.
A parallelogram is a two-dimensional object that you might have already encountered in geometry class. You can recognize a parallelogram by its parallel opposite sides, and also by its opposite angles that are equal. Adjacent angles on a parallelogram always add up to 180 degrees. If the angles of a parallelogram are 90 degrees, then it’s straight up and down, like a square or a rectangle.