The domain is all of the x values in a set and the range is all of the y-values in a set.
If you have a bunch of points such as (3,6), (7,2), (1,5) the domain would be stated as D={3, 7, 1} and the range would be stated as R={6,2,5} If you have a line, then the domain and range would be set up differently. For example, if you have a line with end points at (-3,2) and (5,8) then the domain would be D=(-3,5) and the range would be R=(2,8)