Anupiṭaka is a fancy word in Buddhism that means "something that is not touched by impurities". It's like when you have a brand new toy and it's super clean and shiny. Anupiṭaka is like that toy, it's super clean and pure. But instead of a toy, it's talking about the Buddhist teachings that are pure and haven't been changed or mixed with other ideas.
You know how sometimes when you play with your toys, they get all dirty and mixed up with other toys? That's kind of like how some people mix different ideas and beliefs together, which can change the teachings of Buddhism. But anupiṭaka means that the teachings are still pure and haven't been mixed up with anything else.
It's important to have anupiṭaka because it helps us understand the true teachings of Buddhism without anything else getting in the way. It's like having a clear mind to understand things better.