A doctrine of Catholicism is that you need good works as well as faith in order to get into Heaven. When Martin Luther broke away and started the Protestant movement, one of the big changes he made was to drop the “good works” part so that faith alone is sufficient to get into Heaven. (As I understand it, the argument behind this is that Jesus saves us from all of our sins already so therefore it does not matter how good or bad we are during our lives as long as we have faith.)