What is Ethereum? A plain guide to ETH and how it works

Ethereum is a public blockchain that runs software. It launched on July 30, 2015, at 3:26:13 PM UTC. Its coin, ether (ETH), pays the fees that keep the network running and rewards the people who help secure it. Bitcoin was built to move money. Ethereum was built to run programs. No middleman.

The official project puts it plainly. Ethereum is "a decentralized blockchain network and software development platform, powered by the cryptocurrency ether (ETH)," according to ethereum.org. In plain terms, it is a shared computer that no single company controls. Anyone can read it. Anyone can build on it. Once code is live, it keeps running whether or not its author sticks around.

Ether (ETH): the fuel, not the money alone

Ether is the coin that powers everything on the network. You need it to do anything that changes the blockchain, from sending funds to using an app. Every action costs a small fee, paid in ETH. People call this the gas fee. Think of it as the toll for using a shared road. The busier the road, the higher the toll.

Its smallest unit is called a wei, and fees are often quoted in gwei, which is a billion wei. You do not need to track that day to day. What matters is the idea. Every write to the blockchain has a price, and that price rises and falls with demand. When lots of people want in at once, fees climb. When things go quiet, they drop.

Ethereum.org describes ether as "a new kind of digital money you can send to anyone, anywhere in the world in seconds for as little as a few cents." That is the simple use. The deeper one is fuel. Validators, the computers that check and add new transactions, must lock up ETH to take part. In return they earn ETH rewards. By market value, ether has for years ranked second only to bitcoin.

Smart contracts and the apps built on them

A smart contract is a program that lives on the blockchain and runs on its own. Once it is deployed, it does exactly what its code says, every time, and no one can step in to change the outcome. Ethereum.org calls these "open-source programs" that let anyone "create their own digital assets and decentralized applications (dapps) that run 24/7, globally."

Picture a vending machine. You put in the right coins, you get the item, and no cashier is involved. A smart contract works the same way, only with digital money and data. Developers stack these contracts into full apps. Lending markets, trading venues, games and marketplaces all run this way.

Two everyday examples show the range. Most stablecoins, the dollar-pegged tokens covered in our guide to what actually backs a stablecoin, live as smart contracts on Ethereum. So do the automated pools that many people now trade through instead of a traditional exchange order book. The code holds the money and follows the rules, and the same rules apply to everyone.

What people build on Ethereum

Most of the activity falls into a few buckets. Decentralized finance, or DeFi, rebuilds lending, trading and saving with code instead of banks. Stablecoins move dollars around the clock. Non-fungible tokens, better known as NFTs, record who owns a specific digital item, from art to event tickets. Some groups even run themselves through code, in what people call a DAO, where token holders vote on decisions.

None of this needs a bank's permission. That is the pitch, and part of it is real. It is also messy. Many projects fail, some are outright frauds, and the same openness that lets anyone build lets anyone build badly. Treat the word "decentralized" as a question to check, not a promise to trust.

Most tokens you hear about live on Ethereum too. They follow a shared standard, so wallets and exchanges can handle them the same way. To use any of it, you need a wallet, which is really just a place to hold your keys and sign actions. Lose the keys and you lose the funds. No password reset exists.

For all the noise, real use has grown. Stablecoins on Ethereum settle large sums every day, and firms have started to test tokenized versions of funds and bank deposits on public chains. That does not make every project sound. It does mean the base layer is more than a playground now.

How Ethereum agrees on the truth: proof of stake

Every blockchain needs a way for thousands of strangers to agree on one shared record. Ethereum used to do this with mining, the same power-hungry method Bitcoin still uses. That changed in 2022.

On September 15, 2022, Ethereum finished an upgrade called the Merge. It swapped mining for proof of stake. Instead of racing to solve puzzles with costly hardware, validators put up ETH as a deposit and get picked to add blocks. Cheat, and they lose part of that deposit. The switch cut the network's energy use by about 99.95 percent, according to ethereum.org, a figure TechCrunch reported on the day it happened.

This difference between the two methods is worth understanding on its own, and our explainer on proof of work versus proof of stake walks through it. Proof of stake is greener. It is not perfectly decentralized. A handful of large staking providers now control a big share of the ETH that secures the chain, which worries some researchers.

Staking is open to regular users, within limits. Running your own validator takes a fixed deposit of ETH and some technical skill. Most people instead join a staking service or a pool and hold a token that stands in for their staked coins. That is easier. It also adds a layer of trust, since you lean on whoever runs the service to play fair.

Ethereum next to Bitcoin

People often ask which is better, Bitcoin or Ethereum. That framing misses the point. They were built for different jobs. Bitcoin aims to be sound digital money, with a strict supply limit and a deliberately simple design. Ethereum aims to be a platform for programs, and it changes far more often.

Two more differences stand out. Bitcoin still runs on mining, while Ethereum switched to staking in 2022. Bitcoin also caps its total supply at a fixed number, while ether has no hard cap, a design choice that shapes how each coin is used and valued. Both points matter more to a long-term holder than to someone sending a payment this afternoon.

For a newcomer, the practical read is simple. Want a plain store of value, and people point to Bitcoin. Want to use apps, tokens or DeFi, and that activity mostly happens on Ethereum and networks like it. Neither choice is a bet you have to make. Plenty of people hold both, for different reasons.

A short history, from idea to upgrade

Ethereum began as an idea from Vitalik Buterin, a young programmer who thought Bitcoin's design was too narrow for what code could do. The mainnet went live on July 30, 2015. Early releases were bare and aimed at developers, not the general public. Wider use came later, as tools improved and more people learned to build.

Moving to proof of stake took years. A separate test chain, the Beacon Chain, started on December 1, 2020, and ran alongside the main one before the Merge joined them in 2022. Buterin, an Ethereum co-founder, called the Merge "a big moment for the Ethereum ecosystem" and said everyone who helped "should feel very proud," TechCrunch reported.

Upgrades keep coming. They do not follow a fixed calendar, and no one can promise when the next one ships. That is normal for open software run by a scattered mix of volunteers and companies. Plans slip. Features get dropped. What ends up on the chain is what the network agrees to run.

What can go wrong: the risks and limits

Decentralized does not mean safe. A smart contract is only as good as its code, and a single bug can drain millions in minutes. Once money leaves your wallet, there is usually no refund and no support line to call. The same finality that makes the network hard to censor makes mistakes hard to undo.

Fees can spike. When the network is busy, a simple transaction can cost far more than a few cents, which is the opposite of the cheap ideal. Newer networks built on top of Ethereum, known as layer 2s, try to bring those costs down, with mixed results so far. Scams are common, and a convincing app can hide a draining contract.

Then there is price. Ether moves hard in both directions, and past gains say nothing about the future. None of this is financial advice. It is the plain risk picture anyone should hold in mind before touching the network.