When you create a new table, you can change the cell spacing and the cell padding. Ever wonder what the difference is between the two? The easiest way to find out is to make a new, 4x4 table and then change just the cell spacing to 30 and set the cell padding to 0. Then apply. See what happened? Now switch the values and apply it again. See a difference?

In a nutshell, cell spacing adds a border around the outside of cells and cell padding adds space inside a cell.