Blockchain technology is a distributed ledger system that records transactions across a network of computers in a way that is transparent, immutable, and decentralized. Ethereum's blockchain is the most widely used smart contract platform in the world, processing millions of transactions daily while maintaining 100% uptime since its launch in 2015.
The Ethereum blockchain consists of a chain of blocks, each containing a set of validated transactions. When a user initiates a transaction — such as sending ETH, interacting with a smart contract, or minting an NFT — it is broadcast to the network, validated by nodes, and added to a new block. Each block references the previous block's cryptographic hash, creating an immutable chain of records that cannot be altered without redoing all subsequent blocks.
Since the Merge in September 2022, Ethereum uses Proof-of-Stake (PoS) consensus. Validators stake 32 ETH as collateral and are randomly selected to propose and attest to new blocks. Honest validators earn ETH rewards; malicious validators risk having their staked ETH "slashed" (partially destroyed). PoS reduced Ethereum's energy consumption by approximately 99.95% compared to the previous Proof-of-Work system.
Layer 2 networks are built on top of Ethereum to increase transaction throughput and reduce costs. Optimistic rollups (Arbitrum, Optimism) and ZK-rollups (zkSync, StarkNet, Polygon zkEVM) batch thousands of transactions off-chain and submit compressed proofs to Ethereum's mainnet. The Dencun upgrade (2024) introduced EIP-4844 "proto-danksharding," reducing Layer 2 fees by up to 90%.
"The blockchain technology section is incredibly detailed. I finally understand how Ethereum consensus works!"
"Layer 2 explanation is the clearest I have seen anywhere. Highly recommended for anyone learning about Ethereum scaling."
"Great technical depth without being overwhelming. Perfect for intermediate crypto enthusiasts."
