When people call bitcoin a “digital currency,” they’re missing the point. The euro is a digital currency, the US dollar is a digital currency. Less than 8 percent of these currencies exist in physical form; the rest is bits on ledgers. But the fundamental difference is that these ledgers are controlled by centralized organizations, whereas in bitcoin, they’re not. Bitcoin has a decentralized network, an open network. ​

Antonopoulos, Andreas M.. The Internet of Money