Resoftening is needed when food hardens and you need it soft again. These are usually sugar based consumables. There is an easy way to make them soft again. Just seal them in an air tight plastic bag or container with a fresh slice of bread. By the next day they should be soft. The harder the item the longer the wait, and you might need to use more than one piece of fresh bread. Things I have resoftened are: cookies, brown sugar, and Peeps. It might work with marshmallows too.
Rehardening is needed when something wilts and you need it hard again. These are usually vegetables. There is an easy way to make them crisp again. Just put them in a container and cover the item with cold water. Refrigerate for a few hours and you will have crunchy veggies once again. By the way, this is a great way to keep the veggies crunchy, too. Things I have rehardened are: carrots, radishes, and celery. It might work for peppers, too.