A cryptocurrency is a digital asset that exists on a blockchain — a shared, continuously-updated ledger maintained by a network of independent computers rather than a single bank or company. Bitcoin, launched in 2009, was the first working example of this idea; thousands of other cryptocurrencies have since been built on variations of the same underlying concept.

What makes a blockchain different from a normal database

A traditional bank ledger is controlled by the bank — they can update it, and you have to trust them to do so honestly. A blockchain instead distributes copies of the ledger across many independent computers ("nodes"), and new entries (transactions) are only added when the network reaches agreement that they're valid, through a process called consensus. Once a transaction is recorded and confirmed, it becomes extremely difficult to alter — every subsequent block on the chain reinforces the ones before it.

This is what people mean by "decentralized": no single company or government runs the ledger, and no single party can unilaterally rewrite it.

Coins vs. tokens

"Bitcoin" refers to both the network and its native currency. Many other blockchains — like Ethereum — support building additional assets ("tokens") on top of the base network, which is why you'll see thousands of different cryptocurrencies with very different purposes: some function purely as money, others represent ownership, access, or participation in a specific application or protocol.

Volatility is a defining feature, not a bug

Crypto markets trade 24/7, have far shorter histories than traditional currency or equity markets, and often have less liquidity — all of which tends to produce larger and faster price swings than most traditional assets. That volatility is central to why crypto gets attention, and also why the risk-management principles covered elsewhere in this section apply here with, if anything, extra weight.