Any cryptocurrency that is not Bitcoin and is therefore considered an alternative option to the earliest digital currency.
An altcoin is simply any digital currency that is not Bitcoin. The term evolved from a combination of ‘alternative’ and ‘virtual coin,’ thus referring to any and every digital currency that is not the earliest and traditional cryptocurrency, which is Bitcoin. Moreover, an altcoin is no longer defined solely as virtual currency, but also includes the entire spectrum of crypto tokens and other crypto-related assets which use a different Blockchain algorithm and network than Bitcoin.
Some of the most common and innovative altcoins in blockchain history are Ethereum (ETH), Tether (USDT), ChainLink (LINK), Dogecoin (DOGE), and Kyrrex (KRRX). Each of these altcoins is different from Bitcoin in terms of operational algorithm and deployment (allocation) structure.