Yes. The above post is correct. I dunno how keen you are as far as math or basic geometry goes, but think also like this: Draw a square (or rectangle, triangle, etc) on a piece of paper. You are working in 2 dimensions, length and width. Now picture floor space. Same thing. Length and width. Represented by this: ft². When you are talking about square feet/inches/miles, etc, you are caulculating only length and width. A 2 dimensional space.
Volume is where the 3rd dimension comes in. Height. Think of the square again. Now add the height aspect. You now have a box. Not 4 sides, but 6. When you measure all three dimensions and multiply them together, you come up with the volume the box can hold (liquid, styrofoam peanuts, sand, etc). This is shown as cubic measurement: ft³.
Hope I didn't confuse you.