What is a Coinbase on-chain send?

Could you please elaborate on what exactly is meant by a "Coinbase on-chain send"? I understand Coinbase is a popular cryptocurrency exchange platform, but how does the term "on-chain send" specifically apply in this context? Is it a type of transaction that occurs directly on the blockchain, as opposed to an off-chain or peer-to-peer transfer? And what are the key characteristics or advantages of using a Coinbase on-chain send for cryptocurrency transfers?