metamorworks/iStock via Getty Images Talk about digital currencies is heating up after the ECB launched the investigation phase of its digital euro project. However, many are still asking how the tender would differ from the electronic money we use today via credit cards, online banking and popular payment app Venmo (PYPL). Definitions first... While there are many descriptions of "digital currencies," they are broadly broken down into three categories. Decentralized cryptocurrency: These are unregulated offerings like Bitcoin (BTC-USD), Ethereum (ETH-USD), Ripple (XRP-USD) and Dogecoin (DOGE-USD). Since they are issued by a network, and not any central authority or government, they are often volatile, but can also be exchanged for goods or services like traditional currencies. Cryptos often use distributed ledger technology (like blockchain) that can confirm valid tokens and log transactions. Stablecoins: These also use distributed ledger technology, but they attach the value of tokens to something that already exists.