Similar to Bitcoin, Ethereum transactions are peer-to-peer transactions. Transactions in Ethereum can be made externally by a user or a contract. They each consist of different parts: a none, the number of transactions sent by the user; recipient, use who receives the amount of Ether sent and identified by an address; the amount of ether, the value sent from user to another user; data, optional; signature of the sending user, necessary to validate the coins; value start gas, limit of execution steps; value gas-pas, the fee that has to be paid to miner per steps.