The word “altcoin” is an abbreviation of “BitcoinBitcoin is a digital currency (also called crypto-currency) ... More alternative,” and thus describes every single cryptocurrencyA cryptocurrency (or crypto currency) is a digital asset des... More except for Bitcoin. Altcoins are referred to as Bitcoin alternatives because, at least to some extent, most altcoins hope to either replace or improve upon at least one Bitcoin component. There are over 400 altcoins in existence. The most popular ones are Litecoin, Etherium, and Dogecoin.