What is Diamond Storage?

From the Diamond Standard:

Since Solidity 0.6.4 it is possible to create pointers to structs in arbitrary places in contract storage.

This enables diamonds and their facets to create their own storage layouts that are separate from each other and do not conflict with each other, but can still be shared between them.

Learn more about Diamond Storage:

Understanding Diamonds on Ethereum

New Storage Layout For Proxy Contracts and Diamonds