The domain is the set of values you can put in for x. And the range is the set of vaules you get out of the function. On a graph f(x) against x, the difference in x values shows the domain and the range of y values gives you the range. Example: If f(x) = x2 , the domain (values we put in for x) can be any real number, R. But, x2 is always going to be positive, so the range of this function is f(x) >= 0 .