Three answers, and folding is usually right
The rule
Against a re-raise you can fold, call, or raise again. Most of your opening range does none of the last two.
You opened with a range built for a table that had not acted yet. Somebody behind you raised, which means their range is now far stronger than the one you opened against. The hands that were comfortable opens are not automatically continues.
Position decides how much survives. In position you can call with hands that flop well and see what happens, because you will act last for the rest of the hand. Out of position that same call turns into guessing on three streets, so the range narrows sharply and more of it becomes fold or raise with nothing in between.