The Ethereum is a network of open and decentralized blockchains that also produces a cryptocurrency: the Ether, also called ETH.
Bitcoin is a money transfer system invented in 2009. Through a peer to peer network, it achieves total decentralization. Learn everything about Bitcoin here.
Tether (USDT) is not much different than with any other cryptocurrencies.
So what is Tether, this stable cryptocurrency and why is it pegged to the dollar?