Attention this is not a repeated talk, functions versus variables is one wonderful relationship in a variable sometimes independent, beside it plays some specials in independent variables statistics it almost essential, let us define it x in here, or sometimes dependent, you find more about it in dependent variable definition, let us define it y or Y in here, y depends on x and x does not depends on y in the relationship y=f(x), sometimes we go and plot a profile and sometimes go and make a table.