Ethereum Concepts

Foundational reference for Ethereum and EVM-compatible chain development. Covers the mental models that every other skill assumes you know — gas, transactions, storage, ABI encoding, and the execution environment. This is not a tool skill; it is the conceptual substrate beneath all EVM tooling.

What You Probably Got Wrong

LLMs confidently generate Ethereum code with fundamental misconceptions. These are the ones that cause real bugs.

• Gas is not ETH — Gas is a unit of computation. You pay gasUsed * effectiveGasPrice in wei. Confusing gas units with ether amounts is the most common mental model failure.
• Transaction types are not interchangeable — There are four types (0, 1, 2, 3). Type 2 (EIP-1559) is the default since London. Each has different fields and fee semantics. Sending a legacy (type 0) transaction still works but uses the old fee model.
• Nonce is per-account and sequential — Skipping a nonce blocks all subsequent transactions. There is no way to "fill" a nonce gap except by sending a transaction with the missing nonce. Nonces start at 0 for EOAs and at 1 for contracts (post-EIP-161).
• msg.value is in wei, not ETH — 1 ether in Solidity is 1e18 wei. Passing 1 as msg.value sends 1 wei (0.000000000000000001 ETH), not 1 ETH.
• Storage slots are 32 bytes — Every slot holds exactly 32 bytes. Smaller types are packed within a single slot when declared adjacently. Understanding this is critical for gas optimization and direct storage reads.
• Contract addresses are deterministic — CREATE uses keccak256(rlp(sender, nonce)). CREATE2 uses keccak256(0xff ++ sender ++ salt ++ keccak256(initCode)). Same inputs always produce the same address, even before deployment.
• address(0) is not a burn address by design — It is the zero address. Tokens sent there are irrecoverable, but it has no special EVM semantics. Some protocols use it as a mint/burn signal by convention.
• block.timestamp is set by the block proposer — It must be greater than the parent timestamp and within ~15 seconds of real time. Do not use it for tight time comparisons or as entropy.

Gas Mechanics