The main functions of money are typically presented as being a medium of exchange, a unit of account, and a store of value.
Many forms of money have emerged historically but by the end of the 20th Century nearly all money was issued by government as legal tender. This is called fiat money.
Cryptocurrency is an emergent application of distributed ledger technologies that becomes accepted as offering a medium of exchange, a unit of account, and a store of value, i.e. money.
It is a social construct insomuch as the mechanism is considered to have monetary value because everyone else considers it to have monetary value.
Governments may offer fiat cryptocurrencies in the future, so-called central bank digital currency (CBDC).