BSC is a blockchain with it's own ecosystem similar to the Ethereum blockchain. There's a great page from Binance which explains what the Binance Smart Chain is here: https://academy.binance.com/en/articles/an-introduction-to-binance-smart-chain-bsc
You can read more about how this benefits Mogul and why it makes sense to operate on multiple blockchains here: https://intercom.help/mogul-productions/en/articles/5340235-why-are-stars-tokens-on-multiple-blockchains