Transaction
A transaction is an instruction signed by your private key and sent to the network — "send 0.1 ETH to this address," "swap these tokens," "call this contra
A transaction is an instruction signed by your private key and sent to the network — “send 0.1 ETH to this address,” “swap these tokens,” “call this contract.” Nodes validate it, it waits its turn in the mempool, and once confirmed it’s permanently part of the ledger.
Why it matters
Transactions are how everything on a blockchain actually happens, and they’re final — no refund center, no chargeback, no undo. That finality is both the power of the model and the reason care is needed: sign once, verify forever.