Calculate the area of a rectangle

The area is how much space the rectangle takes up. The length $l$ is one side, and the width $w$ is the other side, at a right angle to the length.

The formula is:

$$A = l \cdot w$$

You multiply the two sides by each other. Think of it as small 1 by 1 squares: each row holds $l$ squares, and there are $w$ rows in total. That is why the area is $l \cdot w$.