While Bitcoin introduced the world to decentralized digital currency, Ethereum expanded blockchain technology into something much broader: a programmable global computer. Understanding what Ethereum is and how smart contracts work explains why so much of the modern crypto ecosystem is built on top of it.
What Is Ethereum?
Ethereum is a blockchain platform designed not just to record who owns what, but to execute code. Instead of a ledger limited to currency transfers, Ethereum's blockchain can run smart contracts — self-executing programs that carry out predefined instructions automatically whenever their conditions are met, without needing a bank, escrow agent, or other intermediary to enforce them.
What Are Smart Contracts?
A smart contract is simply code deployed to a blockchain. Once deployed, it runs exactly as written, and the outcome is enforced by the network itself rather than by trust in a counterparty. For example, a smart contract could automatically release funds to a seller the moment predefined conditions are verified on-chain, without either party needing to trust the other directly — the code, and the decentralized network validating it, does the enforcing.
This programmability is what enables the broader category of decentralized applications (dApps) — software that runs on a blockchain instead of a company's private servers.
What Ether (ETH) Is Used For
Ether, Ethereum's native asset, serves two main roles. It functions as a tradeable digital asset in its own right, and it is also used to pay for computation on the network — a fee commonly referred to as "gas." Every action on Ethereum, from a simple transfer to executing a complex smart contract, requires a small amount of ETH to compensate the network for the computing resources used.
What Ethereum Enabled
Ethereum's smart-contract capability unlocked an entire ecosystem beyond simple payments:
| Category | What it enables |
|---|---|
| Decentralized finance (DeFi) | Lending, borrowing, and trading without a traditional bank — see [what DeFi is](what-is-defi-decentralized-finance) |
| Non-fungible tokens (NFTs) | Unique, verifiable ownership of digital or tokenized assets — see [what NFTs are](what-are-nfts) |
| Decentralized exchanges | Peer-to-peer trading without a centralized order book operator |
| Decentralized autonomous organizations | Group coordination and voting governed by code rather than a traditional corporate structure |
From Proof of Work to Proof of Stake
Ethereum originally secured its network using proof of work, the same general approach as Bitcoin, relying on computational mining. It later transitioned to proof of stake, in which validators lock up ETH as collateral to participate in confirming transactions, rather than competing with computing power. Our guide to proof of work vs proof of stake explains the tradeoffs between these two consensus approaches in more depth.
Risks Specific to Smart Contracts
Beyond the general volatility and custody risks shared across cryptocurrency, Ethereum-based applications introduce contract-level risk: flawed or maliciously designed code can be exploited, sometimes resulting in irreversible loss of user funds. Established, audited, widely used protocols generally carry lower — though never zero — risk than obscure or brand-new ones.
Common Mistakes
- Assuming "smart contract" means "risk-free" or "guaranteed correct."
- Interacting with unaudited or unfamiliar decentralized applications without research.
- Confusing Ethereum the platform with Ether the asset.
- Ignoring gas fees when evaluating the cost of using Ethereum-based applications.
Conclusion
Ethereum turned blockchain from a ledger for currency into a platform for programmable, trust-minimized applications. Smart contracts are the mechanism that makes this possible, powering everything from decentralized finance to NFTs. Understanding this distinction — Ethereum as infrastructure, Ether as its native asset, and smart contracts as the applications built on top — is essential to understanding much of the modern crypto ecosystem.