Transactions are signed messages originated by an externally owned account (EOA), transmitted by the Ethereum network, and recorded on the Ethereum blockchain. Another way to look at transactions is that they are the only things that can trigger a change of state, or cause a contract to execute in the EVM. Ethereum is a global singleton state machine, and transactions are what make that state machine "tick", changing its state. Contracts don't run on their own. Ethereum doesn't run autonomously. Everything starts with a transaction.

📌 The Structure of a Transaction

The basic structure of a transaction, as it is serialized and transmitted on the Ethereum network. Each client and application that receives a serialized transaction will store it in-memory using its own internal data structure, perhaps embellished with metadata that doesn't exist in the network serialized transaction itself. The network-serialization is the only standard form of a transaction.

A transaction is a serialized binary message that contains the following data:

Nonce

• A sequence number, issued by the originating EOA, used to prevent message replay (double-spending).

Gas Price

• The price of gas (in wei) the originator is willing to pay.

Gas Limit

• The maximum amount of gas the originator is willing to buy for this transaction.

Recipient

• The destination Ethereum address.

Value

• The amount of ether to send to the destination.

Data

• The variable-length binary data payload.