A batch of verified transactions recorded on a blockchain.
Detailed Explanation
A block is a fundamental unit of data in a blockchain. Each block contains a collection of verified transactions, a timestamp, a reference to the previous block (creating the 'chain'), and a unique identifier called a hash. When a new block is created, it must be validated by the network through the consensus mechanism (proof of work, proof of stake, etc.) before being permanently added to the blockchain. Block size and block time vary by network — Bitcoin produces a block approximately every 10 minutes with a 1 MB size limit, while Ethereum produces blocks every 12 seconds.
Why It Matters
Blocks are the foundational building blocks of all blockchain networks. Understanding how blocks work helps you comprehend transaction confirmation times, network congestion, gas fees, and scalability challenges. Block size and block time directly affect a blockchain's throughput (transactions per second) and overall performance.
Real-World Example
When you send Bitcoin to someone, your transaction is broadcast to the network and sits in a 'mempool' waiting area. A miner includes your transaction in the next block they're building. Once that block is validated and added to the chain, your transaction has one confirmation. Most exchanges require 3-6 confirmations (blocks) before crediting your deposit.