BNB Chain, the BNB currency's home. It is designed for lightning-fast trading. To do this, it had to make certain trade-offs, one of which was that it was not as versatile in terms of programmability as other blockchains.
The Binance Smart Chain, a new blockchain with a full-fledged ecosystem for developing high-performance decentralized applications, is here to change that. It was designed to be cross-chain interoperable, to ensure that users get the best of both worlds.
The Binance Chain, rebranded BNB Beacon Chain in 2022, was launched in April 2019 by Binance.
Here is a great resource for learning more about the Binance smart chain blockchain APIs.