On the Bitfinex exchange, you can use the "Exchange" and "Margin" wallets for trading. "Margin" is a wallet for trading in which you use funds borrowed from the exchange.
"Exchange" is a classic exchanger. With it, you change the base cryptocurrency to another cryptocurrency. To do this, in the "Settings" section, you choose not only the wallet type, but also the base currency.
The base currency is the one that you change to get a different currency.