Any function in math has a set of numbers you can input, and the set of numbers you get out.The numbers you input are called independent variables and the numbers you get out are called dependent variables--they depend on what you put in.For example, in the function f(x) = x+1, if you input a 0 (the independent variable) you get out a 1 (the dependent variable).The word "domain" is another term for all the numbers you can input (the idependent variables).The word "range" is another term for all the numbers you get out (the dependent variables).Hope that helps.