The definition of cryptocurrency is a digital or virtual currency that is secured by cryptography, which makes it nearly impossible to counterfeit or double-spend.

Cryptocurrencies rely on a distributed ledger system to record transactions. The authenticity of each transaction is protected by digital signing. Security measures are typically built into the related cryptocurrency design.

Bitcoin, for instance, employs proof-of-work for currency validation and uses asymmetric cryptography as well as elliptic curve cryptography. For its security, Bitcoin makes heavy use of public-key cryptography and has a large but not entirely complete script written in JavaScript.

All cryptocurrencies share some common features:

They are not controlled by a central authority. There is no government, company, or person in charge of any cryptocurrency. Cryptocurrencies are open-source networks and every developer is free to participate. No single entity can inflate the currency by issuing more of it. Every cryptocurrency user is free to determine if they will accept any new currency that is issued.

Cryptocurrencies use a distributed ledger system to record transactions. They are open-source networks operated by the users who hold the currency.

If you know what a cryptocurrency is, you know the value of it. Cryptocurrencies are valued based on their popularity and demand in the market. If there is no demand for a cryptocurrency, then it will eventually become worthless and go out of circulation. If people have no need for something, they will not be interested in it or buy it.