“Plenty of things, usually to cast spells and perform magic,” Harry answers further, “Well, if they try to use a wand that doesn’t fit them, it would cause an assortment of chaos. Very few wizards and witches can use various wands without worrying about them backfiring in them.”

He knows that very well since he had to rely using different wands to cast spells when his old wand broke for a good while and he manages to survive using said different wands without them backfiring on him.