Many crypto guides start at “buy the dip.” This one starts one step earlier, because if you do not know what a coin actually is, every number you meet later — price, volume, the results of any backtest — is a word you cannot check.
A coin is a balance on a shared ledger
There is no file on your computer holding a bitcoin. What exists is a ledger — a record that many independent machines keep a copy of and agree on.
Bitcoin’s own documentation says the network is “sharing a public ledger called the ‘blockchain’,” that this ledger “contains every transaction ever processed,” and that coins “are appended to a public ledger that is shared between all the devices on the network” (bitcoin.org FAQ). Your balance is not a stored number so much as what that transaction history adds up to.
What “owning” means depends on who holds the key
The same page says users control funds through “digital signatures corresponding to the sending addresses” (bitcoin.org FAQ). Whoever can produce that signature can move the balance.
That splits into two very different situations, and beginners are almost always in the second one:
- Self-custody — the key is yours. Nobody can move your balance, and nobody can restore it if you lose the key. There is no password reset because there is no company holding your account.
- Custodial — you bought on an exchange and the exchange holds the key. You have an account with a company, with a password you can reset. What you own is a claim on that company, not the ledger entry itself.
Neither is “correct.” They are different risks, and knowing which one you are in is the first thing worth being sure about. The next article in this track is about exchanges, which is where most people meet the custodial case.
Supply is a rule, not a promise
Some coins cap how many will ever exist. Bitcoin does: new issuance halves over time “until bitcoin issuance halts completely with a total of 21 million bitcoins in existence” (bitcoin.org FAQ).
That cap is a rule written into software the network agrees to run. It is not a guarantee of price and says nothing about demand. A fixed supply with no buyers is still worth nothing.
Other coins use other rules. Ethereum burns the base fee of every transaction — it is “burned during the transaction process, removing it from circulation” — and at high enough fee levels that burn can bring “net ETH inflation to zero or less for that day” (ethereum.org — Issuance). So its supply can move in either direction depending on how busy the network is. The point is not which rule is better. The point is that the rule is a published property of that specific coin — something to look up rather than assume.
A coin is not a company — and not everything on a coin list is a coin
A share of a company is a claim on its future earnings. A coin like bitcoin has no issuer and no earnings: its price is whatever the next buyer pays. That is not a criticism, it is a description — the tools built for stocks (earnings, book value, dividend yield) have nothing to attach to.
But be careful with the word “coin.” Exchanges now list perpetual contracts that track things which do have earnings — tokenized stock and commodity perps. On our own coin index you will find symbols like SAMSUNGUSDT and SKHYUSDT alongside BTCUSDT; those track listed companies, and their pages carry a “tokenized stock perp” notice for exactly this reason.
So the honest version is: a coin has no issuer behind it, unless the thing it tracks does. Check what you are looking at before you apply either mental model.
What a coin is, on this site
Here a “coin” is narrower and more concrete: a symbol the backtest engine can actually run, because it has hourly open/high/low/close/volume history. That history is the raw material for everything else on this site.
The coin index can be a slightly wider list than that — if a symbol ever appears there without a usable hourly history, the simulator refuses it rather than inventing one. If a symbol runs, it has the history; if it has no history, nothing here will pretend otherwise.
That is the whole reason the basics matter. A strategy is a rule applied to that history. If you do not know what the history is — a record of what people paid, on a ledger nobody owns — you cannot judge whether a backtest on it means anything.
What you should be able to say now
- A coin is a balance on a shared ledger, and moving it requires a key.
- Whether you hold that key, or a company holds it for you, is a different question from what the coin is.
- Supply follows a published rule, and that rule is not a price promise.
- A coin has no issuer behind it — unless it is tracking something that does.
If those make sense, the next question is: where does that price actually come from? That happens on an exchange, and how an exchange matches buyers to sellers decides what your order really costs.