What a cryptocurrency actually is
A cryptocurrency is a digital asset secured by cryptography and recorded on a blockchain, transferable without a bank sitting in the middle. That definition covers wildly different things — a decades-long store of value, a programmable platform, a price-stable payment token. Here's how to tell them apart.
Not all coins are trying to do the same job
| Type | Example | What it's for | Defining trait |
|---|---|---|---|
| Bitcoin | BTC | Store of value, censorship-resistant payments | Fixed supply of 21 million; the original, 2009 |
| Programmable platforms | Ethereum (ETH) and similar | Running smart contracts, DeFi apps, NFTs | Native asset pays for computation ("gas") |
| Stablecoins | USDT, USDC | Moving value on-chain without price swings | Pegged to a reserve asset, usually the US dollar |
| Altcoins | Hundreds of others | Everything from niche utility to pure speculation | Wide, uneven quality — verify before assuming legitimacy |
Your wallet doesn't hold coins — it holds keys
Coins aren't "stored" in a wallet app the way cash sits in a physical wallet. The ledger itself — the blockchain — is where ownership is recorded. A wallet just holds the cryptographic keys that let you prove ownership and authorize transfers.
Every wallet has two paired keys, and mixing them up is the single most common source of costly mistakes:
Public key / addressLike a bank account number. Safe to share — it's what people send funds to.
Private keyLike the signature that authorizes a transfer. Anyone who has it can move your funds — never share it, screenshot it, or type it into a site that emailed you first.
Custodial vs. non-custodial, at a glance
Custodial (exchange wallets)
An exchange holds your private keys on your behalf, similar to a bank holding your cash. Convenient for trading, but you're trusting that company's security and solvency.
Non-custodial (self-custody)
You hold your own private keys, in software or on a dedicated hardware device. Full control — and full responsibility; lose the keys or the recovery phrase, and there's no customer support line to call.
Cold storage
Keeping keys entirely offline — a hardware wallet or even paper — so they're never exposed to an internet-connected device. Common for holdings you don't touch often.
Volatility is a feature of the market, not a glitch
Crypto markets trade continuously, sit on comparatively thin liquidity next to major stock markets, and react fast to news, regulation, and shifts in sentiment. That combination produces price swings far larger and faster than most traditional assets typically see in a single day.
None of that tells you whether a specific asset is a good or bad holding right now — that depends on facts and judgment this site isn't in the business of supplying. What's worth understanding is the mechanism: thin order books plus continuous, global, sentiment-driven trading equals sharper moves in both directions.
What an exchange is actually doing
Order matching
Exchanges match buyers and sellers, in crypto much like a stock exchange matches trades — the trade itself doesn't touch the blockchain until you withdraw.
Fiat on/off ramps
They convert between traditional currency and crypto, which is where most people's first exposure to a blockchain actually happens.
Custody and compliance
Regulated exchanges hold assets on your behalf and follow identity and reporting rules — a different trust model from holding your own keys.
Ran into a term you didn't recognize?
The glossary covers gas fees, forks, market cap, and more.