I've been confused for a while on what happens to a particular cryptocurrency when swapped to another. I mean when a swap may be BNB to get usdt, what happens to the BNB?
Another confusion I have is about BTC.
BTC has a total supply of 19,495,156 million. Now the entire 19,495,156 are in circulation which means they are being held by holders/users. But another user can always swap another coin to BTC at anytime and receive the BTC, so where is the BTC coming from since it already in circulation (held by other holders)?
Every exchange centralized or decentralized holding a well amount of token in the wallet for this purpose and whenever you swap any token you will get your desires token while your own token goes to their wallet. This is the reason DEX offers liquidity reward for this purpose. You can check this by own experience in the low quality fast exchange like fixedfloat. When you send payment, you can check that address holding all that coin which they offering for swap.
Btc answer is also same, Big amount of btc holding by these exchanges. circulation supply also composed of exchange holding. when we swap, we receive btc from these exchanges and at the same times other user sell btc and whole system works in this way.