What Is Ethereum? Smart Contracts and the World Computer

If Bitcoin is digital gold, Ethereum is closer to a global, decentralized computer. Launched in 2015 by Vitalik Buterin and a team of co-founders, Ethereum took Bitcoin's core idea — a shared, tamper-resistant ledger — and made it programmable. That single change unlocked an entire economy of applications.

From currency to platform

Bitcoin's scripting is intentionally limited; it's optimized to do one thing — move bitcoin — extremely securely. Ethereum's creators wanted a blockchain where developers could write arbitrary programs that run exactly as written, with no possibility of downtime, censorship, or third-party interference.

These programs are called smart contracts: self-executing code deployed to the blockchain. A smart contract can hold funds, enforce rules, and automate outcomes. "If X happens, release the money to Y" — without a bank or escrow agent in the middle.

Ether, gas, and how it runs

• Ether (ETH) is Ethereum's native currency. It's used to pay for computation and as a store of value and collateral across the ecosystem.
• Gas is the unit that measures computational work. Every action — sending ETH, swapping tokens, minting an NFT — costs gas, paid in ETH. When the network is busy, gas prices rise (you can watch them live on our gas tracker).
• The EVM (Ethereum Virtual Machine) is the runtime that executes smart contracts identically on every node, keeping the whole network in agreement.

Proof-of-stake: the Merge

Originally Ethereum, like Bitcoin, used energy-intensive proof-of-work mining. In September 2022, in an upgrade known as the Merge, Ethereum switched to proof-of-stake. Instead of miners burning electricity, validators lock up (stake) ETH as collateral and are chosen to confirm blocks. Misbehave, and your stake is slashed. The change cut Ethereum's energy use by over 99% and made ETH issuance much lower.

What people build on Ethereum

Ethereum's programmability gave rise to whole categories of crypto applications:

• DeFi (decentralized finance) — lending, borrowing, trading, and earning yield without banks. See our DeFi guide.
• Stablecoins — dollar-pegged tokens like USDC and USDT that live as smart contracts. See stablecoins explained.
• NFTs — unique tokens representing art, collectibles, identity, and more.
• DAOs — internet-native organizations governed by code and token holders.

Most other "smart contract platforms" — and thousands of tokens — were directly inspired by, or built to compete with, Ethereum.

Layer 2: scaling Ethereum

Ethereum's security and popularity come with a cost: limited throughput and, at times, high fees. The ecosystem's answer is Layer 2 networks (rollups) — separate chains that process transactions cheaply and in bulk, then post compressed proofs back to Ethereum for final security. They let users transact for a fraction of the cost while inheriting Ethereum's guarantees.

Strengths and trade-offs

Strengths: the largest developer community in crypto, deep liquidity, battle-tested security, and an enormous ecosystem of applications and tooling.

Trade-offs: base-layer fees can spike during demand, the technology is complex, and competition from faster Layer 1s is fierce. Ethereum's roadmap leans heavily on Layer 2s to address scale.

The bottom line

Ethereum turned the blockchain from a ledger into a platform. ETH powers the network, smart contracts automate trust, and a sprawling ecosystem of DeFi, stablecoins, and NFTs runs on top. If you want to understand most of modern crypto, you have to understand Ethereum.

Educational content only — not financial advice.