The currencies used for transactions on the blockchain are called cryptocurrencies. There is enough discussion in the market already, calling cryptocurrencies assets, commodities, digital gold, or even similar to real estate. Cryptocurrencies are digital currencies that operate as a medium of exchange on a peer-to-peer level and enable direct payments between individuals. Since the entire blockchain is developed using asymmetric cryptography principles, it would be wise to call Bitcoin or any mode of exchange on the blockchain a cryptocurrency. The idea behind this invention is to find a way to be independent of a central authority while producing a secure, immutable and verifiable means of exchange. They run on a decentralized platform, which means it is not controlled by any central authority. The decentralized nature of blockchain makes cryptocurrencies theoretically immune to old ways of government control and interference. Transactions made through this system can neither be reversed nor forged. Cryptocurrencies are a solution to the problem of digital cash and help maintain integrity. As we all know, the first cryptocurrency was Bitcoin, launched in 2009, and its inventor, Satoshi Nakamoto, remains unknown to this day. Bitcoin's success has given rise to a number of competing cryptocurrencies, known as "altcoins." Today, there are literally thousands of cryptocurrencies in existence, with a combined market capitalization of over $270 billion. Bitcoin currently accounts for over 50% of the total market value.

Here is the original link to the Bitcoin white paper that started this revolution.

https://bitcoin.org/bitcoin.pdf