Collection 2 of 5 · 7 cards
Blocks & network
A blockchain is kept by many computers talking to each other. This collection follows a transaction from the moment it is signed, through the waiting room of the mempool, into a block — and explains how blocks are linked, starting with the very first one.
Cards in this collection
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What is a node?
A node is any computer that runs a blockchain's software, keeps a copy of its data and exchanges new transactions and blocks with other nodes.
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What is a peer-to-peer network?
A peer-to-peer network is a network in which computers connect directly to each other as equals, sharing data without routing it through a central server.
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What is a blockchain transaction?
A blockchain transaction is a signed instruction, broadcast to the network, that asks for the shared record to be changed in one specific way — for example, moving units between addresses or calling a smart contract.
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What is the mempool?
The mempool, short for memory pool, is the waiting area in which a node keeps valid transactions that have been broadcast but not yet included in a block.
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What is a block?
A block is a batch of transactions bundled together with a header and added to a blockchain as one unit, once the network accepts it as valid.
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What is a block header?
A block header is the small summary at the top of every block — exactly 80 bytes in Bitcoin — that links the block to its parent and commits to all of its transactions.
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What is a genesis block?
The genesis block is the first block of a blockchain — block number zero — which has no parent and is written directly into the network's software instead of being produced by consensus.
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