I've always thought that physics is best explained through analogies, and so instead of two resistors we'll imagine two people (our resistors) in Yo Sushi (where plates of sushi represent our voltage). Say the first person, person A, is twice as hungry as person B (A has twice the resistance of B) . This means that for every 3 plates, A will take 2 of them and B will take 1. We can imagine taking the voltage across A, which is counting the number of plates A has. It will always be 2/3 of the total number of plates. Similarly, looking at B will show 1/3 of the plates. A question often asked in exams is what is the voltage 'in between' A and B, a Vout placed between them. This is simply looking at the amount of sushi left on the conveyer belt after A has taken theirs. If A's taking 2/3 of it all, only 1/3 will be left and hence Vout = 1/3. By altering the ratios of the resistances (or how hungry person A is) you can change Vout and that is all there is to a potential divider.