Most explanations of crypto come from someone who wants you to buy some, or from someone who wants you to be afraid of it. Neither is a good teacher. This guide does the thing that is oddly rare: it explains what the technology is, in plain terms, so that whatever you decide afterwards is decided by you.
Nothing here is a recommendation to buy, hold or avoid anything. It is how it works.
A ledger with no owner
Start with a bank. Your account balance is a number in the bank’s ledger. The bank controls the ledger, you trust the bank to keep it honestly, and a regulator watches the bank. That arrangement has worked, mostly, for centuries.
A blockchain is a ledger with the middle taken out. Instead of one organisation holding the record, thousands of computers around the world each hold a copy, and they agree between themselves, by a fixed set of rules, which transactions are valid and in what order. No single party can alter the history, because everyone else’s copy would disagree. That is the entire idea, and everything else is built on it.
“Block” and “chain” are literal: transactions are bundled into blocks, each block references the one before it, and changing an old block would break every block after it. That is what makes the record hard to tamper with.
Coins, tokens, and what you actually own
A coin is the native unit of a particular blockchain: the thing the network’s rules are written around. A token is something built on top of an existing blockchain, using its infrastructure, and there are hundreds of thousands of them, most of them worthless.
When you “own” a coin, what you actually hold is a private key: a very long secret number that proves the right to move a balance recorded on the ledger. The coin is not in your wallet in any physical sense; it is a line in the shared record, and the key is what lets you write the next line.
That leads to the sentence that should be tattooed on every new entrant: whoever holds the key holds the coins. Lose the key, and there is no “forgotten password” link, no branch to visit, no regulator to complain to. The balance is visible on the ledger forever and nobody can ever move it again. A meaningful fraction of all the coins ever created are in exactly that state.
Wallets: the word is misleading
A wallet is software (or a small device) that stores keys and lets you use them. Two kinds matter.
A self-custody wallet means you hold the keys yourself. Total control, total responsibility. Nobody can freeze it; nobody can help you if you lose it or if you are tricked into sending from it.
A custodial wallet means someone else holds the keys for you, usually an exchange. This is what most people actually have when they “buy crypto on an app”, and it means the coins are, in practice, theirs to hold on your behalf. Which brings us to the most important distinction on this page.
An exchange is not a bank
An exchange is a business where you can swap ordinary money for crypto and back. When you leave a balance there, it is held by the exchange, in its systems, under its terms.
It is not a bank. In most places it is not covered by a deposit guarantee scheme, the kind that protects a bank account up to a fixed sum if the bank fails. Several large exchanges have failed, and customers have found that the balances they thought were theirs were a claim in a bankruptcy, paid out years later at a fraction of their value, or not at all. The EU now has a dedicated regulatory regime for crypto-asset businesses; what it does and does not protect is worth reading before assuming anything.
The practical rule the industry itself uses: not your keys, not your coins. A balance on an exchange is a promise from a company, and the company’s promise is only as good as the company.
How transactions are agreed
For a ledger with no owner to work, the computers running it have to agree on which transactions are real. That agreement is called consensus, and different blockchains reach it differently.
Some use proof of work: computers race to solve a hard computational puzzle, and the winner adds the next block and is rewarded with new coins. This is “mining”, and it is why some blockchains use as much electricity as a small country.
Others use proof of stake: participants lock up coins as a deposit for the right to add blocks, and lose the deposit if they cheat. Far less energy, different trade-offs.
You do not need to understand either in depth. You need to know that “the network confirms your transaction” means “enough of these computers have agreed”, that it takes time, and that once agreed it cannot be reversed. There is no chargeback in crypto. A payment sent to the wrong address, or to a fraudster, is gone.
What “decentralised finance” means
DeFi takes the no-owner idea further: instead of a company offering lending, borrowing or trading, a piece of software on the blockchain (a smart contract) does it automatically, with no one in charge. It is genuinely novel, and it has genuinely lost people enormous sums, because a bug in the software is a bug with nobody to call, and because “no one in charge” also means no one responsible. That is Module 13 of the course, and it has four risks of its own.
What this guide is not
It is not a case for or against. Some of this technology is remarkable; a great deal of what has been built on it is speculation, and some is fraud. Understanding how it works is the only reliable way to tell which is which when someone is describing it to you enthusiastically.
Where this fits
This is Module 14 territory in our Financial Literacy Course, alongside Module 7 on how modern payments and e-money actually work, and it leads directly into the four risks nobody mentions and spotting the scams that target you online, because crypto is where most of them now live. For the technology side of what we build, see our Technology hub.
Educational guidance, not regulated financial advice, and not a recommendation to buy, hold or sell any crypto-asset. Crypto-assets are high-risk, largely unprotected, and you may lose everything you put in. Nothing here replaces advice from a regulated adviser who knows your full circumstances.