The domain is all the values of x that are to be used. This relation has ordered pairs, for each one the number on the left belongs to the x-value of the pair and the number on the right belongs to the y-value of the pair.
For the relation {(3,2)(5,3)(6,4)(8,10)}
Domain: {3, 5, 6, 8}
Range: {2, 3, 4, 10}