This video teaches how to simplify finding the area of a rectangle by breaking it down into smaller rectangles. It explains how to use decomposition to turn one of the side measurements into smaller, easier-to-multiply numbers. The video provides step-by-step instructions and examples to show how this method can be applied to different rectangle measurements. It also emphasizes that there are multiple ways to decompose a number and encourages viewers to pick the method that makes the most sense to them.