Ethereum specifically: the world computer and its rollups
Ethereum is where most of crypto beyond Bitcoin actually happens. Understanding its account model and its rollups explains most of what you will meet.
Accounts, not UTXOs
Ethereum works the way you would expect: addresses have balances, and a transaction subtracts from one and adds to another. Simpler to reason about, and it makes programs far easier to write, which is the point.
The EVM, in plain terms
The Ethereum Virtual Machine is the environment every contract runs in. Every node executes the same instructions and must reach the same answer, which is what makes the result trustworthy without a referee.
The EVM became a de facto standard. BNB Chain, Polygon, Avalanche, Base, Arbitrum and dozens more are "EVM compatible", meaning contracts written for Ethereum run there with little or no change. That is why your Ethereum address works on all of them and why MetaMask can add them so easily.
Why gas exists at all
If computation were free, anyone could publish a contract containing an infinite loop and halt the network. Gas prices every operation, so an infinite loop simply runs until the sender's gas is exhausted and then stops. Gas is a denial of service defence first and a fee market second.
What the Merge actually changed, and what it did not
In September 2022 Ethereum switched from proof of work to proof of stake. Energy consumption fell by over 99 percent, and issuance dropped sharply because validators cost far less to pay than miners did.
Rollups, explained properly rather than just called cheaper
A rollup is a separate chain that executes transactions off Ethereum, then posts a compressed record of them back to Ethereum. Ethereum stores the data and settles disputes. You get Ethereum level security at a fraction of the cost, because thousands of transactions share one mainnet posting.
What this means practically
- Use a rollup for anything routine. The same swap costs dollars on mainnet and cents on Base or Arbitrum.
- Mainnet still matters for large amounts, where the fee is small relative to the value and you want maximum security and liquidity.
- Each rollup is its own environment. Its own liquidity, its own token deployments, its own bridge. A token on Arbitrum is not automatically the same token on Base.
- Optimistic withdrawal delays are real. Plan around the challenge window or accept a third party bridge's fee and risk.
Where Ethereum is going
The stated roadmap is explicitly rollup centric: Ethereum aims to be the settlement and data availability layer while execution happens on rollups. Upgrades since 2024 have focused on making data posting dramatically cheaper for rollups, which is why layer 2 fees fell so sharply.
BEFORE YOU MOVE ON
Common questions
What is the EVM?
The Ethereum Virtual Machine, the environment every smart contract executes in. It became a standard, which is why dozens of other chains are EVM compatible and your Ethereum address works on them.
Did the Merge make Ethereum cheaper?
No. It cut energy use by over 99 percent and reduced issuance. Fees are set by demand for block space, and cheap transactions came from rollups instead.
What is a layer 2?
A separate chain that executes transactions and posts a compressed record back to Ethereum, inheriting its security while costing far less. Arbitrum, Base and Optimism are the largest.
Why does withdrawing from Arbitrum take seven days?
Optimistic rollups assume batches are valid and allow a challenge window for fraud proofs. Waiting it out is free; third party bridges will front you the funds sooner for a fee.
Risk warning: crypto is highly volatile and largely unregulated. You can lose everything you put in. Nothing here is financial, investment or tax advice.