Cryptocurrencies are electronic peer-to-peer currencies. They don't have any physical representation. In many instances, cryptocurrencies are used to pay for transactions fees on a blockchain.

The Ethereum blockchain requires users to pay transaction fees in its own cryptocurrency, ether. Even though ether and other cryptocurrencies do not have a physical representation, it does not mean that they are not worth anything. There are people and companies around the world willing to pay a lot of money to acquire cryptocurrencies.