What Ethereum Is and How It Differs from Bitcoin

You already know a blockchain is a shared, append-only ledger — a record of transactions copied across many computers that nobody can secretly rewrite. Bitcoin used that idea to do exactly one thing supremely well: move money without a bank. But here’s the question a few restless developers asked next: what if the ledger could also run programs? Not just “send 3 coins to Bob,” but “send 3 coins to Bob only if it’s after Friday and two other people have signed off.” That single jump — from a ledger that records to a ledger that computes — is what Ethereum is. This lesson is about what that means, why it needs a different design than Bitcoin, and what “programmable money” actually gets you.

A World Computer, Not Just a Cash Register

Think of Bitcoin as a pocket calculator that does one operation flawlessly: move money. You can press the buttons, but you can’t reprogram it. Ethereum is a general-purpose computer — except instead of running on one chip in one laptop, the same program runs on thousands of independent computers around the world, all checking each other’s work and agreeing on the result.

That’s why people call Ethereum a “world computer.” It’s a single, shared, decentralized platform that runs programs called smart contracts — self-executing code that lives on the blockchain and does whatever it was written to do, automatically, with no company hosting it and no off-switch. We’ll dig into how that code actually executes (on something called the EVM) in the next lesson; for now, just hold the picture: Ethereum is a computer the whole world shares.

And every computer needs a way to pay for the electricity. Ethereum’s is ETH — its native coin. You hold ETH like you’d hold any crypto asset, but you also spend it to pay for the computation your programs use. More on that in a second.

Ether (ETH): the Fuel, Not Just the Money

Ether (ETH) wears two hats. The first is the obvious one: it’s a digital asset you can buy, hold, send, and trade, just like any other coin. The second is the interesting one: ETH is the fuel that powers the world computer.

Here’s the logic. Running a program costs real work — thousands of computers each have to execute your code. So Ethereum makes you pay for that work in ETH. The amount you pay for a given chunk of computation is called gas (we’ll cover gas properly in a later lesson; just know it’s the metering system, and you settle the bill in ETH). No fuel, no execution. This isn’t a nuisance — it’s the spam filter and the incentive that keeps a shared computer from being abused.

The units: ETH, gwei, and wei

Because a single ETH can be worth a lot, and fees are often tiny, you need small units. ETH divides into very small pieces, and the smallest of all is the wei:

So 1 ETH = 1,000,000,000,000,000,000 wei (a one followed by eighteen zeros), and 1 gwei = 1,000,000,000 wei. In practice you hold and think in ETH, but whenever you see a fee quoted you’ll see it in gwei — it’s the comfortable middle unit, the way you’d quote a phone bill in cents rather than fractions of a dollar.

Supply: no hard cap (and that’s deliberate)

Here’s a sharp contrast with Bitcoin. Bitcoin has a fixed cap of 21 million coins — scarcity baked in forever. Ethereum has no hard supply cap. New ETH is issued as a reward to the people who help secure the network (through staking — we’ll define it below and in detail later). So in principle the supply can keep growing.

But there’s a twist. Since an upgrade called EIP-1559, part of every transaction fee is burned — permanently destroyed, removed from supply. When the network is busy, more ETH gets burned than issued, so the total supply can actually shrink. Fans nicknamed this “ultrasound money” (a cheeky jab at Bitcoin’s “sound money”). Don’t overthink it yet — the full mechanics come later. The takeaway for now: ETH has no fixed cap, but its net supply is shaped by issuance minus burning, not by a hard ceiling.

Bitcoin vs Ethereum: Same DNA, Different Mission

Bitcoin and Ethereum share the same DNA — both are decentralized, public, append-only blockchains secured by a global network, with no company in charge. But they were built for different missions, and almost every design choice flows from that. Here’s the side-by-side:

A few terms in that table are new, so let’s unpack the three biggest differences in plain words.

1. Capability — limited script vs. full programs. Bitcoin can run small bits of logic, but on purpose it’s kept narrow: mostly “what conditions unlock this coin?” Ethereum is Turing-complete, a fancy way of saying its programs can express essentially any computation — loops, conditions, calling other programs. That’s the whole reason apps can live on Ethereum and not (easily) on Bitcoin. The trade-off: more power means more ways to write buggy or expensive code, which is exactly why gas exists to meter it.

2. Consensus — mining vs. staking. This is how a leaderless network agrees on the ledger. Bitcoin uses proof-of-work: miners burn enormous amounts of electricity racing to solve a puzzle, and the winner adds the next block. Ethereum used to do the same, but in 2022 it switched to proof-of-stake: instead of burning power, participants lock up (“stake”) their own ETH as a security deposit and are chosen to propose blocks; cheat, and they lose their stake. Same goal — honest agreement with no boss — radically different method (and far less energy). Both mechanisms get their own lessons later.

3. Bookkeeping — UTXO vs. accounts. Bitcoin tracks money like a wallet full of distinct bills: you don’t have “a balance,” you have a pile of unspent transaction outputs (UTXOs), and spending means consuming whole bills and getting change. Ethereum instead keeps an account balance, just like your bank statement — a single number that goes up and down. The account model is far friendlier for smart contracts, because a contract needs a persistent place to remember things (its balance, its data) between calls.

Programmable Money, in Plain English

Once money and code live on the same ledger, you can build things that plain cash never could. Here’s the quick tour — each is a category we’ll explore in depth later, so just one analogy each:

• Tokens — a smart contract can mint its own coin, so launching a new currency is like writing a spreadsheet of balances that enforces itself. (Most “coins” you hear about are actually tokens on Ethereum.)
• DeFi (decentralized finance) — lending desks and exchanges that are just programs, like a vending machine for loans and swaps: put coins in, get the agreed result out, no banker approving anything.
• NFTs — a contract that proves this exact digital item belongs to this exact wallet, like a deed of ownership that can’t be forged.
• DAOs (decentralized autonomous organizations) — a club whose bylaws are code: members vote, and the contract automatically does whatever the vote decided, like a treasurer who can only ever follow the written rules.

The slogan you’ll hear is “code is law” — the contract does exactly what it says, every time, and no one can step in to stop it. Beautiful when the code is right. The flip side is just as permanent: if the code has a bug, that executes faithfully too, and there’s no manager to call for a refund.

Myths to Retire

Ethereum collects almost as many confident-but-wrong takes as Bitcoin does. Let’s bin the big ones.

The Big Picture

Ethereum in one frame: a programmable world computer, born to do what Bitcoin’s money-only design couldn’t, fueled by ETH, and unlocking a whole category of applications. Chunk it into one picture:

A mixed recap — it pulls from every section above:

Key Takeaways

You now know what Ethereum is and how it differs from Bitcoin. The natural next question is how the code actually runs: where does a smart contract execute, and how do thousands of computers agree on the result? That’s the job of the EVM, the world computer — our next lesson.