What is Block?
Crypto Glossary Definition
The thing being mined by miners. It's where transactions are stored. Once written, it cannot be altered or removed. It can be thought of like a page in a public ledger.
Why Block Matters
A block is a batch of confirmed transactions bundled together and added to the blockchain — each new block references the one before it, which is what creates the literal "chain" and makes altering old transaction history computationally impractical.
Block in Practice
Think of a busy afternoon on the Ethereum network, where thousands of pending transactions - token swaps, NFT mints, loan repayments - are sitting in the mempool waiting to be processed. A validator selected to propose the next block gathers a batch of these transactions, orders them, checks that each one is valid, and bundles them together into a single block along with a reference to the previous block's identifier. Once other validators verify and agree on this block, it gets appended to the chain, and every transaction inside it is now considered part of the permanent, shared record that every node on the network holds a copy of. A user who submitted a token swap a few minutes earlier can now see their transaction listed inside this specific block on a block explorer, along with its exact position in the sequence and the exact fee they paid. If someone later tried to alter even one detail of that transaction, they would need to also alter every block built on top of it and convince the rest of the decentralized network to accept the fraudulent version - a practically impossible task given how many independent validators are involved. That immutability, block after block, is what gives the whole chain its integrity.
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