Dollar bulls are those who buy dollar contracts and are in a bullish position.
That is to say, in foreign exchange transactions , investors are optimistic about the US dollar and expect the US dollar to rise, so they buy a certain amount of US dollars at the current price. After a period of time when the US dollar rises, they hedge their contract positions at a higher price to earn profits. Long means that investors are optimistic about the exchange rate and expect the exchange rate to rise, so they buy when the price is low and sell when the exchange rate rises to a certain price in order to obtain the difference.