I don't understand the law of multiple proportions! Help!?

[Queen of the Hobbits]

I am in Chemistry and I don't understand the law of multiple proportions. My textbook states " the law of multiple proportions applies to different compounds made from the same elements. It states that the mass ratio for one of the elements that combines wit ha fixed mass of the other element can be expressed in small whole numbers." I have been reading it over and over and researching it, but I just can't understand it for some reason. Can someone explain, in simple terms, what the law of multiple proportions is? And maybe give an example too?