Ethereum & Smart Contracts: Programmable Money

Ethereum extended blockchains to support general-purpose programs called smart contracts. Contracts execute deterministically on-chain, hold assets, and expose functions that other accounts can call, enabling decentralized applications (DApps) like exchanges and lending markets.

Gas and costs

Every operation consumes gas. Users specify gas limits and fees; the network orders and executes transactions based on supplied fees. Complex contracts that use more computation or storage cost more gas, so efficiency matters.

Security

Smart contracts are code that controls real assets. Prefer audited, battle-tested contracts; understand upgrade and admin controls; and never grant unlimited permissions to unknown contracts.