Digital currency or cryptocurrency (such as Bitcoin) is digital money which can be used for trading (i.e buying and selling other cryptocurrencies and/or fiat currencies) in the same way normal currencies can, e.g. the US Dollar. Although digital currencies or assets cannot be exchanged for physical cash (i.e. notes) it holds value and is accepted as payment similar to how transactions are done via banking apps, online stores or even debit and credit card transactions.
Digital currencies or assets are exciting because they are based on blockchain technology. (Learn more here). Blockchain technology is a new ground-breaking form of transmitting and storing transactions and data that is highly secure and free from third-party control. (Learn more about the advantages and application of blockchain technology here).