What's the different between buying via the "buy crypto" menu VS "trade"

Hey everyone,

Noob question but I'm a little bit confused. When you go under "buy crypto > cash balance" you can buy BTC with your USD. Are those BTC coming from the market or from binance? It doesn't look like you're buying off the market with this option?

Also why do trades on the exchange are BTC/USDT? Like if I were to sell my BTC on the exchange I would get USDT which I would have to transfer to USD if I wanted to withdraw to my bank.

Because Binance allows me to sell my crypto directly via "Buy crypto > cash balance > sell" without going on the exchange. It seems easier or am I missing something?

Thanks