I wanted to send some USDT on the Binance chain but the eallet prompt says I needed some BSC to proceed. What does that mean? Is it the same as BNB?
Yes, it is the same as $BNB. You also have to make sure that the $BNB you have is a BEP-20 token & not BEP-2. The 2 standards are different, if you have the BEP-2 one, you will not be able to process the $USDT transaction you want to make. If you are still confused by all my explanations, you can read the article to find out the differences between the 2 standards here:
https://indodax.com/academy/en/strip-complete-bep20-wallet