| Bitcoin | A digital money system with no central owner. Anyone can verify transactions using open-source rules. |
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| Blockchain | A public history of Bitcoin transactions grouped into blocks. Each new block links to the previous one. |
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| Block | A bundle of verified transactions added to the blockchain. On average, Bitcoin adds one about every 10 minutes. |
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| Proof of Work | The security process where miners spend computing power to create valid blocks. This makes rewriting history very expensive. |
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| Hash | A fixed-size fingerprint of data. Even a tiny data change creates a very different hash. |
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| Hashrate | The total computing power miners are using on Bitcoin. Higher hashrate generally means stronger network security. |
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| Difficulty | An automatic setting that controls how hard it is to mine a block. It adjusts so blocks stay near a 10-minute average. |
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| Halving | An event every 210,000 blocks where new bitcoin issued per block is cut in half. |
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| Block Subsidy | The newly created bitcoin paid to miners in each block. This amount decreases over time because of halvings. |
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| 21 Million Supply Cap | Bitcoin is designed so total supply approaches, but never exceeds, 21 million BTC under current consensus rules. |
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| Satoshi (sat) | The smallest bitcoin unit. 1 BTC equals 100,000,000 satoshis. |
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| Wallet | Software or hardware that stores your keys and lets you send or receive bitcoin. |
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| Private Key | A secret number that proves ownership of bitcoin. Whoever controls it can spend those funds. |
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| Seed Phrase | A human-readable backup of wallet keys (usually 12 or 24 words). If lost, recovery is usually impossible. |
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| UTXO | Unspent Transaction Output. Bitcoin tracks spendable coins as discrete chunks, not account balances. |
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| Mempool | A waiting area for valid transactions before they are included in a mined block. |
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