Crypto is digital money that lives on a public ledger called a blockchain. Whoever holds the private key controls the coins. No bank, no central authority, no physical form. The matrix below compares it to cash, gold and stocks across four properties most people care about. Click any cell to see what each one means.
| Property | Cash | Gold | Stocks | Crypto |
|---|---|---|---|---|
| Supply control | Central bank | Mining | Company | Code |
| Custody | You / bank | You / vault | Broker | You alone |
| Transfer time | In person | Days | T+2 days | 10 min - 24/7 |
| Public verification | No | No | Quarterly | Always, by anyone |
A cryptocurrency is a unit of value that exists as an entry on a shared, public database. The database is updated and protected by cryptography (math), not by a central authority (a bank or government). The first cryptocurrency, Bitcoin, launched in 2009. There are now thousands of them, but the original mechanism is roughly the same for all.
You hold a private key - a long secret number stored in a wallet (an app or a small hardware device). The private key proves you own the address that holds the coins. Lose the key and the coins are unreachable. Share the key and the coins are not yours anymore. This is why how you store crypto is the most important practical decision you will make.
Step 1. Alice opens her wallet and types Bob's address (a string like 1A1zP1eP5QGefi2DMPTfTL5SLmv7DivfNa). She enters the amount, presses send. Her wallet uses her private key to sign the transaction. The signature proves Alice authorized it without revealing the key itself.
Step 2. The signed transaction broadcasts to the Bitcoin network - thousands of computers worldwide. They check that Alice has the coins, that the signature is valid, that she has not double-spent. About every 10 minutes a "miner" bundles valid transactions into a block and adds it to the chain.
Step 3. Bob's wallet sees the new block, finds the transaction to his address, updates his balance. The funds are now his. The transaction is permanent, visible to anyone, irreversible. No bank was involved, no business hours, no approval. Same process at 3 AM Sunday as at 11 AM Tuesday.
Thousands of cryptocurrencies exist. For practical purposes they fall into four buckets. Knowing these covers 95% of what beginners need to recognize.