I take a flat plane piece of paper. I now fold this paper to get a 3-D object. For this 3-D object there is an area. What is this area called in Mathematics?
Consider a plane piece of paper. It has a certain 2-D area. Now fold this piece of paper. What do I get? I get a 3-D object on folding a 2-D paper. The area of paper still remains the same. This area is now able occupy space as a 3-D object. How? The 2-D plane has now become what can be called a ‘surface’ in 3-D. The area of folded paper has now become the area of the surface. This is called ‘surface area’.