Reusable Payment Codes (RPC) are a special way to create bitcoin addresses that can be reused without compromising your financial history, providing bitcoin users with a way to publish payment addresses to the public and keep their transaction history private.
RPC was first proposed a year ago in BIP-47. And one wallet in particular, the Samourai Wallet has been working on integrating it into their UI. Samourai Wallet is a newer wallet that is focused primarily on user privacy, giving users full control over their wallet and funds with features such as Tor support, ‘stealth mode’, and now RPC support.
In a new demo video from the wallet developers, they walk you through a transaction using a reusable payment code. In the video you will see them add a payment code from another Samourai Wallet to open a channel with their wallet. Once the channel is open it will send bitcoin directly to the wallet without ever asking for a bitcoin address. You can share your payment code with the public, it is permanent and never changes. Anyone who adds your payment code will be able to send bitcoin directly to the wallet without asking for a bitcoin address.
You can learn more about how Samourai Wallet is implementing RPC into their wallet here. The current wallet is in public opt-in alpha testing.