Note that all currencies are digital (USD, EUR, etc), I'm assuming you are asking about crypto.
In Mainstream econ, money is a numeraire, which means that it's not a commodity like gold or corn, but rather a token with no consumption or investment use, that is agreed upon as an instrument for conducting all exchange and is fixed in supply (generally by the gov). Folks in the crypto space tried to create the numeraire (a ledger where a token for exchange can exist and bank or gov money is peripheral, rather than the other way around). Except that BTC, for example, has a real input requirement in order to exist (energy). If crypto had no input requirement, it simply existed like a phantom, then it would have the properties of a numeraire.
There are lots of interesting perspectives on crypto, many conflicting one another, which makes it a very large topic. One of the best places to start on the topic would be Desan, because coinage and crypto are similar in that the quantities are [generally] fixed, and we have thousands of years of data on coinage economic systems. Crypto addresses many of the problems identified with coinage: [nearly] infinite divisibility, no loss through wear, and it cannot be diluted [recoined], these are common examples of issues people bring up related to coinage.
Because metal content in coinage in early UK was usually fixed compared to the continent, as the crown made explicit their support for creditors (owners of real wealth and holders of coin). The population generally never owned any coinage and it was not used in exchange where the price of goods and services required breaking the coins into pieces so small that they were easy to lose or be destroyed quickly through use. Typically instead of using coinage, simple IOUs were arranged within local communities, based in the unit of account (coinage). Coinage was used mostly for conducting large trade, often long distance trade. Given a growing population, the purchasing power of a fixed stock of coinage had a tendency to rise, which led to hoarding and outflows from Britain toward the continent, where it was regularly recoined and diluted by reducing the amount of metal per coin in order to create more coins for circulation at a value specified by the state. If the value of the metal in the coins was worth more somewhere else due to a redenomination (dilution), people would melt coins down for the metal and take it there, leaving the domestic population without any coinage for settling IOUs or paying taxes. This lead to compeitive redonominations between states who needed coinage to make payments related to war. When the quantity of coinage in the UK economy fell, it reduced economic activity and the outcome was a great deal of innovation in finance in Britain between the crown and creditors facing shortages of metal and war demands, such as gov borrowing, tally sticks, and later bank notes.
The holders of coin in Medieval Britain successfully fought against dilution in order to maintain their own power to command real resources. The crown had an opposite interest in ensuring the real resources it wanted or needed could be acquired. When the value of coin was too high, the crown would benefit by ordering that only newly minted money was valid and require all old coins be brought to the mint for recoining (making them 'current'). By creating more coins (reducing weight or adding other metal) than what was brought to them, the crown could create tokens for themselves for making payments. The gov did not have to source the metal, as coining was a monopoly of the crown, people dug it up or collected coins and brought it to the mint.
At play here is a dynamic between a state, which needs things and is the sole issuer of money, and holders of those coins, who do not have legal authority to command resources like the crown does, instead they use the money issued by the state. Diluting and issuing coinage was a source of income for the crown (seigniorage) and a means to correct imbalances between the need for coin to conduct exchange, a growing population, prices, and a fixed supply of metal.
If crypto is adopted, like any foreign currency outside control of the state, it means that state no longer has to power to fund itself through money issuance, and in many respects can be summarized as a removal of state sovereignty: the capacity of the state to govern is reduced.
Central Bank Digital Currencies (CBDCs) fall into two broad categories: Account-based and Hardware-based tokens. If a CBDC is created in the form of accounts, this means you and I have access to reserve deposits on the Fed ledger, either directly, or via some private provider who organize the interface to the central bank's ledger. This means you can hold cash in an online account at the Fed. Digital cash. A Hardware-based token CBDC is essentially cash on a hardware wallet. You load it just like you put cash in your wallet, and those tokens are Fed liabilities, just like cash.
Hardware-based tokens are anonymous, like cash. Account-based CBDCs are just like online banking with the Fed. If cash is eliminated then the Fed can push rates negative, and you can't remove your money from the bank, as cash no longer exists. The idea is that by pushing rates negative, and taking money our of your account every day, it compels people to spend their money. Which is false. The desire to save increases as rates become more negative, such as in Germany.