The actual square of the color box can be calculated, and the six sides of the box can be expanded to measure the length and width of each side. The area of each face is long by wide. Adding up the areas of six faces is the area of a box. If the top, bottom, left and right surfaces, and front and rear surfaces have the same area, even if the three surfaces add up and multiply by 2. Rectangular area = length x width. The surface of an object, the size of a plane figure, is called its area (representing the size of a two-dimensional plane figure), which makes the definition language truly reveal the essential attributes of things, which is more logical, because "surface" is a kind of "trace" of "length, width and height", and this trace does not have to be "plane".