The video teaches the viewer how to find the area of a parallelogram and the area of a triangle. For a parallelogram, the first step is to find the right angle, the line perpendicular to the base (this is a line you draw, not part of the parallelogram). The height of the line that forms this right angle with the base is the perpendicular height. Next, find the length of the base. The area is the base times the height. For a triangle, find the right angle with the base (again a line you draw). The height of this line gives perpendicular height. The area of the triangle is the length of the base times the height, divided by two.