Poloniex does not have fiat pairs look to Kraken instead.
So what does the chart "BTC-USDT" means?The idea is to be able to exchange your cryptocurrencies to USDT so that you have something stable to trade against.
However, USDT has been off the rails since this crypto boom started a couple of months ago, and is no longer pegged to the dollar at all. Actually it's been all the way to $0.92 and all the way up to about $1.10 (higher on some exchanges).
I personally wouldn't trust it with your funds and would trade with dollars directly if you want to trade altcoins to fiat (through Kraken for example).
