Transaction
A signed instruction to transfer value or interact with a smart contract, broadcast to the blockchain network.
A blockchain transaction is a data packet signed with a private key that instructs the network to change its state — most commonly by moving tokens between addresses or calling a function in a smart contract.
On Ethereum, a transaction includes the sender address, recipient address, value (ETH), gas limit, gas price (or max fee), and input data (for contract calls). It is broadcast to the mempool, picked up by validators, included in a block, and eventually confirmed.
Transaction finality varies by chain: Bitcoin requires 6 confirmations (~1 hour) for high-value transfers; Ethereum is considered practically final after 2 epochs (~13 minutes); Layer 2s and newer chains achieve near-instant finality.