According to a research produced by Cambridge University in 2017, there are between 2.9 million and 5.8 million unique users actively using a cryptocurrency wallet, most of them using bitcoin. The number of active users has grown significantly since 2013 (there were 0.3 to 1.3 million unique users at the time). Bitcoin is the largest of its kind in terms of total market value.

What exactly is bitcoin?
The word bitcoin occurred in the white paper that defined bitcoin published in 2008. It is a compound of the words bit and coin. It is a cryptocurrency and an electronic payment system invented by an unidentified programmer, or group of programmers, under the name, Satoshi Nakamoto. Nakamoto introduced bitcoin on 31st October 2008 to a cryptography mailing list, and released as open-source software in 2009.

The system is peer-to-peer, and transactions take place between users directly, without an intermediary. These transactions are verified by network nodes and recorded in a public distributed ledger called the blockchain, which uses bitcoin as its unit of account. Since the system works without a central repository or single administrator, bitcoin is called the first decentralized digital currency.

Bitcoins are created as a reward in a competition in which users offer their computing power to verify and record bitcoin transactions into the blockchain. This activity is referred to as mining and successful miners are rewarded with transaction fees and newly created bitcoins.

Besides being obtained by mining, bitcoins can be exchanged for other currencies, products, and services. When sending bitcoins, users can pay an optional transaction fee to the miners. This may expedite the transaction being confirmed.

Over 100,000 merchants and vendors accept bitcoin as payment as of February 2015. Despite the fourfold increase in the number of merchants accepting bitcoin in 2014, the cryptocurrency did not have much momentum in retail transactions.