It's price fixed at the US Dollar. So if I own USDT, I should be able to convert USDT to BTC (e.g.) or paper money. If everyone converts their USDT to paper m

It's price fixed at the US Dollar. So if I own USDT, I should be able to convert USDT to BTC (e.g.) or paper money. If everyone converts their USDT to paper money, the organization that backs USDT has to refund USDT to dollars. If there aren't enough dollars to cover the price of USDT selling, then the USDT market goes belly up. BTC is buy/sell driven through some kind of exchange so the price can float.