USDT is a cryptocurrency based on blockchain and it is said the number of its coins in circulation are backed by traditional currencies e.g. Euro, USD and others but early last year the company behind the Tether announced that its coins are also now backed by loans though admitted they are not 100% backed by dollars.
Fiat currency these are the traditional currencies we use globally e.g. US dollars, Japanese Yen and others and they are issued with the government of their original countries

Benefits of USDT over Fiat
- Freedom with no limitations
- No track record which makes it safer from authorities
- No Government interference
Benefits of Fiat over USDT
- well regulated
- Can be tracked as it has records
- Government has control over it therefore it can control its supply and control inflation
The disadvantages of USDT, money launders and criminals can take advantage of it and do illegal acts transacting with crypto and not tracked but with Fiat the rate of crime is less as compared to Crypto.
Just to be short and precise, USDT is now becoming the safe haven and it saves a lot of time as you will no longer have to go the banking process and it is stress free.