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What is Cryptocurrency?

In short

Digital currency secured by cryptography, on decentralized networks.

Cryptocurrency is digital money that exists as entries on a shared, tamper-resistant ledger called a blockchain, rather than in a bank's private database. With Bitcoin, the first cryptocurrency, no bank checks that you have the funds — a network of independent computers around the world verifies and records every transaction instead.

A blockchain is a distributed ledger maintained by a network of independent computers (nodes) rather than one central authority. New transactions are grouped into blocks, verified through a consensus mechanism such as proof-of-work or proof-of-stake, and cryptographically linked to the previous block — which is what makes past records extremely difficult to alter after the fact. This design removes the need for a bank or payment processor to vouch for a transaction, but it cuts both ways: there is no central institution to reverse a mistaken transfer or a fraud, and no deposit insurance standing behind the balance the way there is for money held at a bank.

Related concepts

  • Bitcoin vs Altcoins — Bitcoin, launched in 2009, was the first cryptocurrency and remains the largest by market value. 'Altcoin' is short for 'alternative coin' and covers every cryptocurrency that came after — from Ethereum, which added programmable smart contracts, to thousands of smaller tokens with widely varying purposes, adoption levels, and track records.
  • Understanding Market Cap — Market cap answers 'how big is this asset, in total?' A cryptocurrency trading at $10 with 1 million coins in circulation has the same $10 million market cap as one trading at $1,000 with 10,000 coins — price alone says nothing about size, which is why market cap, not price, is used to rank and compare cryptocurrencies.
  • Crypto Risks — Crypto risk differs from traditional stock and bond risk in kind, not just degree. Prices can move double digits in a single day, transactions can't be undone once confirmed, and losing access to a private key means losing the funds permanently — there's no customer service line that can reset it.