Bitcoin. First introduced in late 2008, it is a specific currency in an electronic payment system that acts as an alternative to fiat currency. It exists only on computers and the internet. It is not backed by a government, and its price is not set by a centralized authority.
The difference between a digital currency and a cryptocurrency is that the latter is decentralised, meaning it is not issued or backed by a central authority such as a central bank or government. Instead, cryptocurrencies run across a network of computers. Digital currencies have all the characteristics of traditional currencies but exist only in the digital world. They are issued by a central authority.

Now, to be fair to the bitcoin bros (not great) and XRP army (worse), even the World Health Organisation had around that time started pushing the idea that Covid could be being spread by banknotes (while simultaneously recommending that people should not wear masks), now thought to be “very unlikely”. Even if banknotes were a key transmission vector, however, we are not sure that “dirty fiat” itself could be held responsible, given that the vast majority of it only exists in digital form. Why would you use bitcoin, or XRP, or any other crypto token when you can transact digitally using fiat currencies?
The BraveNewCoin aggregated index is chosen as the source of data for Bitcoin, Ethereum and Monero. The BraveNewCoin aggregated index is not used for Litecoin as their index for Litecoin only starts in April 2014 and misses earlier price action. Instead, Litecoin data is retrieved from the BTC-E time series. It should be noted BTC-E has recently (25th July 2017) been shut down by US authorities, however this is after the data interval examined. It has been observed that price differences do exist between cryptocurrency exchanges [19], and it is expected the BTC-E price over time will be different to other exchanges, however with the possibility of exchange arbitrage, prices on different exchanges are reasonably similar.