How to use this page. Read top to bottom the first time. After that, treat it as a
reference and follow the linked pages when you need depth.
A
- Address
- A short string of letters and numbers that funds can be sent to. An address is derived from a public key. Sharing an address does not give anyone the ability to spend the funds at it.
- Altcoin
- Any cryptocurrency other than Bitcoin. The word is descriptive, not a judgement, but the category is enormous and varied. This site is about Bitcoin specifically.
B
- Bitcoin
- Both the network and the unit on the network. Capital B is sometimes used for the network and lower case b for the unit, but usage varies.
- BIP (Bitcoin Improvement Proposal)
- The format used to propose changes to Bitcoin. Numbered, public, and discussed openly. See open source.
- Block
- A bundle of confirmed transactions added to the chain roughly every ten minutes on average.
C
- Confirmation
- A transaction is "confirmed" when a block containing it has been accepted by the network. Each subsequent block adds another confirmation. See basics.
- Cold storage
- Keeping keys offline so that an internet-connected device cannot sign transactions on its own. Often paired with a hardware device.
- Custodial
- Describes a service that holds the keys on your behalf. You hold an account; the service holds the actual Bitcoin. Convenient but introduces counterparty risk. See wallet safety.
D
- Decentralised
- Used to describe systems with no single controlling party. Bitcoin is decentralised in the sense that no single party can change the rules or rewrite the ledger.
F
- Fee
- The amount paid to miners to include a transaction in a block. Fees are denominated per byte of transaction data, not per amount sent.
- Full node
- Software that verifies every block and transaction against the rules. Running one is how users personally enforce the network rules rather than trusting someone else to.
H
- Hash
- A short fingerprint of arbitrary input data. Bitcoin uses hashes for block linking, mining, and address derivation.
- Hardware wallet
- A small dedicated device that stores keys and signs transactions, keeping the keys off a general computer. This site does not recommend specific products.
K
- Key (private key)
- A secret number that authorises spending from a given address. Anyone with the private key controls the funds. Anyone without it does not, even if they own the device.
- Key (public key)
- Derived from the private key. Used to verify signatures and to generate addresses. Safe to share in most contexts.
L
- Ledger
- The shared record of all confirmed transactions. Bitcoin's ledger is replicated across every full node.
M
- Mempool
- The pool of unconfirmed transactions waiting to be included in a block.
- Miner
- A participant that proposes new blocks by performing the proof-of-work computation. Miners do not decide the rules; nodes enforce the rules.
- Mining
- The process of producing valid new blocks. It costs energy, which is the point: the energy cost is what makes rewriting history expensive.
N
- Node
- Any participant running the Bitcoin software and verifying transactions against the rules. See also "full node".
P
- Phishing
- An attempt to trick a person into revealing keys, recovery phrases, or login details by impersonating a trusted party. See wallet safety.
- Proof of work
- The mechanism Bitcoin uses to make block production costly, which in turn makes rewriting history expensive.
R
- Recovery phrase (seed phrase)
- A sequence of ordinary words, usually 12 or 24, that backs up a wallet. Anyone with the phrase has the funds. Treat it as the most sensitive piece of information you own.
- Reorg
- Short for reorganisation. When the network momentarily disagrees on the tip of the chain, blocks can be replaced. Deep reorgs are extremely rare.
S
- Satoshi
- The smallest unit of Bitcoin. One Bitcoin is one hundred million satoshis.
- Self-custodial
- You hold the keys, so you hold the funds, with all the responsibility that implies. The opposite of custodial.
- Signature
- A cryptographic proof that the holder of a key authorised a particular transaction.
T
- Testnet
- A parallel network used for testing. Coins on testnet have no value, which is the point.
- Transaction
- An instruction to move funds, signed by the holder of the keys, broadcast to the network, and included in a block when accepted.
U
- UTXO (unspent transaction output)
- The technical unit Bitcoin actually tracks. A wallet's balance is the sum of the UTXOs it can spend.
W
- Wallet
- Software (or a device) that manages keys, builds transactions, and broadcasts them. A wallet does not "hold" Bitcoin in the way a physical wallet holds notes; it holds the keys that authorise spending.
- Whitepaper
- The original short paper that described Bitcoin. Worth reading more than once. See courses.
Words this glossary does not define
The list below is intentional. These terms are common in crypto marketing but are not useful framing for understanding Bitcoin and are out of scope here: "to the moon", "diamond hands", "buy the dip", "alpha", "shill". If a piece of writing about Bitcoin relies on those words, it is probably trying to sell you something rather than teach you something.
What to read next
Pair this glossary with basics for the conceptual spine, wallet safety for the security layer, and faqs for the questions beginners typically ask in the same hour.