What is Bitcoin? - The World of Cryptocurrency
Bitcoin, often described as a cryptocurrency, a virtual currency or a digital currency - is a type of money that is completely virtual.
It's like an online version of cash. You can use it to buy products and services, but not many shops accept Bitcoin yet and some countries have banned it altogether.
However, some companies are beginning to buy into its growing influence.
In October last year, for example, the online payment service, PayPal, announced that it would be allowing its customers to buy and sell Bitcoin.
The physical Bitcoins you see in photos are a novelty. They would be worthless without the private codes printed inside them.