The geometric term for the number of square units needed to cover a surface is called the area of said surface.
the answer is (area)
One, if the square is large enough.
4x
It is the area.
That depends on the surface and the units, but the surface area tells us that infomation.
trapezoid
surface area
It is the surface area of the solid.
It is the area of the surface.
area
The units may be any squared units. It is an area. They may be square inches, feet, yards, miles, metres, kilometres etc.