Ethereum Cookbook

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If you want to change something in the blockchain, you have to create a transaction, which has to be accepted by all participants. As an example, imagine a bank table that lists the balances of all accounts. The transactional nature of the database ensures that if an amount is subtracted from one account, it is always added to the other account. It also ensures that only the person holding the keys to the account can transfer money from it. This is ensured with the process of signing a transaction cryptographically by the owner.

A transaction can include both binary data and Ether. If the target account contains code, that code is executed and the payload (binary data) is provided as input data. If the target account is non-existent, ...