$BTC Based on the ideology of the free market, Bitcoin was invented in 2008 by an unknown person known as Satoshi Nakamoto.[6] Bitcoin began to be used as a currency in 2009,[7] when its application was released as open-source software.[8]:ch. 1 In 2021, El Salvador adopted it as legal tender.[9] It is often viewed as an investment and many scholars have described it as an economic bubble.[10] As Bitcoin is used under pseudonyms, it has been utilized by criminals which has drawn the attention of regulatory bodies leading to its ban in many countries as of 2021. Bitcoin[ar 1] (abbreviated as BTC; symbol: ₿) (in English: Bitcoin) is the first decentralized cryptocurrency. It can be sent from one person to another over the Bitcoin network in a peer-to-peer manner without the need for a third party. Transactions on the network are verified using cryptography and are recorded in a distributed ledger called the blockchain without a central authority overseeing it. Consensus among the nodes is achieved using a computationally intensive process based on proof of work known as mining, which secures the Bitcoin blockchain. Mining consumes large amounts of electricity and has been criticized for the environmental impact of Bitcoin.