A limit for how many bitcoins can be created is built into the system so the value can't be diluted. The maximum amount is just under 21 million bitcoin. There are currently just over 16.7 million in circulation, each of which was worth around $14,000 at the time of writing.
What affects its price?
The price of a bitcoin has jumped up and down since it first entered the mainstream consciousness in 2013. That year prices rose by almost 10,000 per cent before the collapse of Mt Gox, the biggest online bitcoin exchange, sent it crashing.
Prices slowly crept up after that but have since surged again. This is largely put down to regulators appearing to warm to bitcoin and the rise of initial coin offerings - a way for projects to raise money by selling cryptographic tokens similar to bitcoins. Many sceptics believe we are in the middle of a new bitcoin bubble while advocates say we are just beginning to see the rise of bitcoin.
The rise of digital cryptocurrency Bitcoin has been spectacular. Defying dire warnings from governments, regulators and central banks the price has accelerated in recent weeks as an ever-growing base of buyers have piled in.
The chart below shows how the price of Bitcoin (as measured in US dollars) has changed over the past 12 months.
How many people use bitcoin?
The largest bitcoin storage platform, Blockchain.info, claims it has more than 19 million cryptocurrency wallet holders. This has almost doubled from 10 million at the start of 2017.
What is it used for?
Bitcoin is has a range of uses, including funding companies, investing cash and transferring money without fees. It is commonly associated with criminal activity such as drug dealing, cyber crime and money laundering, since it can be near-impossible to tie a bitcoin wallet to any one individual.
Others simply hold their bitcoins, hoping they will accumulate in value and prove to be a lucrative investment. Its price is notoriously volatile, and early investors are now sitting on massive gains.
Should I invest in bitcoin?
Bitcoin is safeguarded against fraud and theft through independent and decentralised set up, as well as being free from transaction fees. It has also given great returns to some investors, with the price jumping from a few dollars at the beginning of 2013 to $1,100 by November. People who invested £2,000 five years ago would now be millionaires.
After a few level years, its dollar price soared again this year, and it has peaked at over $20,000. But the price has also dropped in the past and left people out of pocket.