What is cryptocurrency?

Cryptocurrency is digital money that moves directly between people over the internet, with no bank in the middle. Instead of a bank keeping the record of who owns what, a network of computers keeps a shared record that nobody can quietly edit.

That is the whole idea. Everything else in crypto (the coins, the apps, the noise) is built on top of it.

The problem crypto was built to solve

When you pay someone online today, you are not really sending money. You are asking a bank or a payment company to update its private spreadsheet: take a number off your row, add it to theirs. That works fine until the company freezes your account, charges a fee, or reverses the payment.

Bitcoin’s original paper, written under the name Satoshi Nakamoto, opens with a single goal: a purely peer-to-peer version of electronic cash that lets payments go “directly from one party to another without going through a financial institution.” The hard part was stopping people from spending the same digital coin twice when there is no bank checking. The answer was a shared ledger.

What a blockchain actually is

A BlockchainA shared record of transactions that nobody can quietly edit. is that shared ledger. bitcoin.org describes it as “a shared public ledger that the entire Bitcoin network relies on.” Every confirmed transaction is written into it, and every participant can check it.

Transactions are grouped into blocks. Each new block is linked to the one before it, so changing an old entry would mean redoing every block that came after. On Bitcoin, the computers competing to add those blocks are doing MiningComputers competing to add the next block, paid in new coins. , and bitcoin.org explains that this process keeps transactions in order and makes it hard for any single participant to rewrite the past.

Think of it like a group chat where every message is permanent, numbered, and copied to every member’s phone. You cannot delete a message from everyone’s history just because you control your own phone.

Coins, keys and who owns what

Here is the part most people get wrong. Your coins do not sit inside an app. They exist as entries on the blockchain. What you hold is a Private keyThe secret that proves the coins are yours. : the secret that proves you are allowed to move those entries.

bitcoin.org explains that wallets sign transactions with a private key, and that signature proves ownership and stops anyone from altering the transaction afterwards. Lose the key and the coins stay on the ledger, untouchable. bitcoin.org puts it bluntly: “lost bitcoins remain dormant forever.”

This is why crypto feels so different from a bank. There is no “forgot password” button on the blockchain itself. Whoever holds the key holds the money, which is freeing and terrifying in equal measure. Step 4 of this course, on wallets, covers how to hold keys without losing them.

Not all crypto is the same thing

“Crypto” covers very different projects, and lumping them together causes bad decisions. A few broad groups are worth knowing.

Bitcoin is the first one and the simplest. It is designed mainly as money with a fixed supply. bitcoin.org states that “only 21 million bitcoins will ever be created.”

Ethereum is a network that runs programs, not just payments. ethereum.org calls it “an open, public blockchain launched in July 2015,” and its native coin is ether (ETH). Those programs let people build apps, tokens and markets on top of it.

Everything else ranges from serious engineering projects to coins invented last week as a joke. Most of the scams you will hear about live in this group. The existence of a coin tells you nothing about whether it is useful or honest.

Why does any of it have value?

A coin is worth what other people will pay for it. There is no government guarantee behind it. The FTC says it directly: “Cryptocurrency accounts are not backed by a government,” and they are not insured like dollars in an FDIC-insured bank account.

People value Bitcoin mostly because of its fixed supply and because no single party controls it. People value ETH partly because you need it to use the Ethereum network: ethereum.org explains that every transaction costs a small fee, called gas, paid in ETH. Whether those reasons justify any particular price is a question nobody can answer for you, and anyone who claims they can is selling something.

What you can count on is movement. The FTC notes that a cryptocurrency’s value “can change rapidly, even changing by the hour,” and bitcoin.org itself calls the price of a bitcoin “still very volatile.”

The risks to know before you touch it

Crypto has real uses and real problems. The problems tend to hit beginners hardest, so here they are without the sugar coating.

• Payments are final. The FTC says cryptocurrency payments “typically are not reversible.” Send to the wrong address or to a scammer and the money is usually gone.
• Scams are common. The CFPB found that for about 40% of crypto complaints it handled since October 2018, consumers listed fraud and scams as the main issue (bulletin dated November 10, 2022).
• Platforms can fail. The same CFPB bulletin describes consumers who could not access their funds because of outright platform failures, plus losses from hacks.
• It is not private. bitcoin.org states that “Bitcoin is not anonymous.” Every transaction is visible on a public ledger forever.
• No one owes you a refund. There is no deposit insurance and no help desk for the blockchain itself.

One rule from the FTC is worth tattooing somewhere: “Only scammers demand payment in cryptocurrency.” Another: only scammers guarantee profits or big returns.

What to do next

You now know the core idea: a shared ledger, keys that prove ownership, and coins whose value is set by the market. The next step is to see how the first and simplest version works in detail.

• Read Bitcoin explained to see the shared ledger in action.
• Jump to Crypto wallets explained if you want to understand keys before anything else.
• Learn how to spot crypto scams before you put a single dollar anywhere.