Unit 1 · Level 1 · Block explorers
Under the hood: internals & logs
The transaction you see is just the button-press. When it calls a smart contract, the contract's code runs and can move value on its own, and those moves appear as internal transactions. And contracts write receipts about what they did, called event logs: every token transfer, every swap, every mint leaves one. The real story of a transaction usually lives here.
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What you get asked
You sent 500 USDC to a friend, but the transaction's Value field shows 0 ETH. Where is the token movement recorded?
A token transfer is really a contract call: USDC's contract updates its balances and emits a Transfer event. The explorer reads that log and shows '500 USDC moved'.
Native coin moved by a contract's code during execution shows up as an ___ transaction.
You signed one transaction, but the contract may pay out ETH to three places while running. Explorers list those under 'Internal transactions'.
Put in order what happens when you call a smart contract
One signature, many effects. That's why a single 'swap' transaction can show a whole cascade of transfers underneath.
Why can one single transaction show dozens of internal transfers?
Contracts call other contracts, which call others still. A DEX aggregator trade might touch ten pools, all from your one button-press.
What is an event log, in plain terms?
Logs are public, permanent receipts: 'Transfer: 500 USDC from A to B'. When the Value field says 0 but money clearly moved, the logs are where you look. 🐜
The rest of this unit
The whole ledger is public. Learn to open it and read it.