Bitcoin, BTC, BTC, is on Bitcoin blockchain and you send it on-chain with Bitcoin blockchain. Alternatively you can send and receive it through Bitcoin Lightning Network but it is off-chain.

BNB is a native cryptocurrency of Binance Smart Chain. BNB is different than Binance Smart Chain (BSC) as a first one is a cryptocurrency and a second one is a blockchain.

On Binance Smart Chain (and other altcoin blockchains), you will see some Bitcoin Wrapped tokens but they are not Bitcoin. What you send and receive is Wrapped Bitcoin tokens, not Bitcoin. Those tokens might does not worth any value if their pegs lost.

https://coinmarketcap.com/view/wrapped-tokens/