This is a feature that was added to the Hive blockchain in Hard Fork 26.
Resource Credit Delegation offers the ability to delegate RC without having to do the same with Hive Power. Before this feature was added, to transfer RC over to another account, one had to delegate Hive Power (HP). This affected one's voting weight in addition to altering the ability to interact with the blockchain.
The change now allows for one to delegate RCs which provide the Mana to engage with the chain while maintaining the HP in one's account. This means the ability to influence the reward pool while also earning curation payouts exists.
It is a move that is expect to be vital for applications and project teams. As new users are sign up, they need to have some resource credits to operate. Application can now delegate this while holding onto the HP. This also enhances their ability to claim accounts since that is based upon HP held.