When you wire an array to the edge of a For Loop, it will sequentially index the array for you as it iterates through loops. A While Loop will also do this, but it is much more common on For Loops, hence, For Loops do it automatically whereas While Loops have to be "right clicked" and told to index the array. Get it?
It is like a Pez Dispenser. Every time the loop iterates the neck pops back and you get the next piece of candy. The loop keeps going popping out yummy candy (I don't like the peppermint but I do like orange) until the dispenser is empty. If you have more than one Pez Dispenser then their heads are all tied together so that they pop back simultaniously and cannot do so independently. This has the unfortunate consequence that once one of them runs out you are done even though there are still other Pez Dispensers full of strawberry or grape. Even worse, if one of them is empty then none of their heads can pop back and you get no candy whatsoever!
[Edit: I am trying to be funny and not sarcastic. I hope you don't take it wrong ]