Key Bitcoin Terms

Digital money consists of data files, carrying the risk of being spent twice. Bitcoin resolves this using consensus ledgers verified ~every 10 minutes.

Takes arbitrary input and produces a fixed 256-bit hexadecimal string. Unpredictable and one-way—powers Bitcoin mining puzzles.

A container grouping pending transactions waiting for miners to confirm and chain onto the global ledger.

Computers competing to solve Proof of Work puzzles for the right to append the next block without central oversight.

Newly minted Bitcoins awarded to the winning miner of each block—the origin of every Bitcoin in existence.

A computer running Bitcoin software that independently downloads, stores, and validates all transactions against consensus rules.

An append-only linked list of blocks cryptographically bound together, making historical alteration practically impossible.

When competing chains exist, nodes automatically trust the branch with the most cumulative Proof of Work.

The pseudonym used by the anonymous creator(s) who released Bitcoin in early 2009. Satoshi's true identity remains unknown.

Bitcoin stores funds as discrete unspent outputs locked to addresses rather than account balances.

Derived from the Private Key; shared publicly to allow others to lock payments to your wallet.

A secret 256-bit random number used to sign transactions and authorize spending. Never share with anyone!

A mathematical signature created using a Private Key that proves ownership without revealing the key itself.

Direct computer-to-computer communication without central servers, where all participating nodes are equal.

Any device connected to the Bitcoin P2P network relaying transactions and blocks.

The temporary holding area on nodes where unconfirmed transactions wait before being packed into a block.

The first Bitcoin block ever mined, created on January 3, 2009 by Satoshi Nakamoto.

The 80-byte header containing metadata such as Previous Block Hash, Merkle Root, Timestamp, Target, and Nonce.

A 32-bit random counter incremented by miners millions of times per second to find a valid block hash.

Automatic adjustment every 2,016 blocks (~2 weeks) to maintain a steady 10-minute average block interval.

Every 210,000 blocks (~4 years), the block subsidy is cut in half, enforcing a 21 million hard cap.

A encoded format derived from a Public Key with built-in checksum error detection.

A lightweight stack-based language attached to outputs specifying spending conditions.

The specific elliptic curve math ($y^2 = x^3 + 7$) used for one-way Public Key derivation.

Elliptic Curve Digital Signature Algorithm used by Bitcoin to sign transactions securely.

A 2017 upgrade that moved signature and script data to a separate witness structure, fixing malleability, lowering fees, and expanding block capacity.

A vulnerability where transaction signatures could be modified without invalidating them, causing the TXID to change before confirmation.

A unique 64-character hexadecimal hash identifying a specific Bitcoin transaction on the network.

The cryptographic proof (signatures and public keys) required to spend Bitcoin, stored separately from core transaction data after SegWit.

A block sizing metric introduced by SegWit capping blocks at 4M WU, granting witness data a 75% discount (1 WU/byte vs 4 WU/byte for base data).

Soft forks are backward-compatible upgrades where non-upgraded nodes stay on the same chain; hard forks introduce incompatible rules risking chain splits.

Software or hardware device managing private keys and addresses. It does not store coins directly, but creates and signs transactions on the blockchain.

A wallet running on internet-connected devices (mobile apps, desktop). Convenient for daily small spending, but more exposed to online threats.

A dedicated physical device keeping private keys strictly offline. Keys never touch the internet, offering maximum security for long-term savings.

A master sequence of 12 or 24 words generated during wallet setup that derives all private keys. Crucial for restoring your wallet on any device.

A classic warning emphasizing that if you leave coins on an exchange where you don't control the private keys, you don't truly own them.