The door shelves on your fridge provide you with somewhere to store your bottles and sauces.
With regular use, these shelves can sometimes break and end up in pieces.
If a door shelf gets damaged, it may give way and thus no longer be suitable for the purpose it was designed for. Door shelves can end up getting cracked or misshapen and thus no longer able to hold bottles and other items.
They can also end up breaking off completely when this happens.
See the range of different types of door shelves available here. You're sure to find the right one to fit your refrigerator.