The crypto coins. Binance is a Crypto to Crypto exchange. You can't deposit or withdraw USD from Binance.
[1] https://www.binance.com/en/support/faq/how-to-buy-cryptos-wi...
Gives you a warm, fuzzy, secure feeling that everything is perfectly safe doesn't it?
I doubt there is anything preventing Binance from doing whatever they want with the coins you place in their possession.