Tether USD or USDT is stable coin in cryptocurrency. The value stable following real USD value. they backed up by actual assets, including USD and EUROS. I dont know what is it but is good to save your coin on USDT. And dont worry about legality. USDT already verified with International Certificate.
This stable coin can you see in many platform exchange, DeFi, or NFT. You no need to worry your assets saved on USDT currency because there are so many corporate or project to be cooperated with.