Bitcoin is a type of digital currency (cryptocurrency). Similar to traditional currencies, like the dollar, pound or euro, there are many types of digital currencies. Other popular ones include Ethereum and Dogecoin. Unlike traditional currencies, though, Bitcoin is not backed or controlled by centralised financial institutions. Instead, it is decentralised. This makes it popular for people who think decentralisation can bring financial freedom, but it also makes it extremely volatile – rising and falling in value at the whim of Bitcoin buyers and sellers.