What is Aldi's bag rule?

I'm curious about Aldi's bag rule. Can you explain what it is and how it works? Do customers need to bring their own bags or does Aldi provide them? If they do provide bags, are they free or do customers have to pay for them? And if customers forget their bags, are there any consequences or penalties? It would be great to get a clear understanding of Aldi's policy on this matter.