Unit 1 · Level 2 · Ethereum & the EVM world
Accounts & gas
Ethereum has two kinds of accounts. An EOA (externally owned account) is controlled by a person holding a private key; that's your wallet. A contract account is controlled by code, not a key. And every single action, from sending ETH to minting a token, burns 'gas', a meter of computational work. No gas, no action.
Free to play. No ads, no token, no account needed to start.
What you get asked
What's the real difference between an EOA and a contract account?
EOAs act when their key-holder signs; contracts act when someone calls their code. Both can hold ETH and tokens.
Why does EVERY action on Ethereum cost gas?
Gas pays the thousands of machines that execute your transaction. It also means flooding the network with junk gets expensive fast.
Your total fee = gas used × gas ___.
Gas units measure how much work your transaction needs; the gas price is what you pay per unit of work. Two dials, one fee.
A simple ETH transfer uses 21,000 gas. If the gas price is 10 gwei per unit, what is the total fee in gwei?
21,000 × 10 = 210,000 gwei. A gwei is a billionth of an ETH, so that's 0.00021 ETH: small when the network is quiet, painful when it's not.
Match each gas concept to its meaning
The work needed is fixed by what you're doing; the price per unit is set by demand. When the network is packed, that second dial is what stings. 🐜
The rest of this unit
A gas-powered world computer, and the standard half of crypto copied.