How does USDT work? An issuer, Tether, creates new tokens when clients deposit traditional money and destroys tokens when clients redeem them. The issuer says each token is backed by reserves of cash, short term government debt and other assets, and it publishes regular reports on them. Redemption at full value is offered mainly to large verified clients; everyone else trades USDT on exchanges at whatever the market pays, which usually sits very close to the target value. The tokens live on public blockchains, so USDT can be sent like any other coin.
How to buy USDT usually comes down to two routes. A regulated exchange is the first: the buyer opens an account, verifies identity and funds it by card or bank payment, then keeps the coins there or withdraws them to a personal wallet. The other route is a person to person deal inside the exchange, where the platform keeps the coins locked until the seller confirms the payment arrived. Such deals carry their own traps, from money that turns out to be stolen to counterparties who ask to finish the trade outside the platform, where no protection is left.