A transaction is a signed data package to transfer ether from an account to another account or to a contract, invoke methods of a contract, or deploy a new contract. A transaction is signed using ECDSA (Elliptic Curve Digital Signature Algorithm), which is a digital signature algorithm based on ECC. A transaction contains the recipient of the message, a signature identifying the sender and proving their intention, the amount of ether to transfer, the maximum number of computational steps the transaction execution is allowed to take (called the gas limit), and the cost the sender of the transaction is willing to pay for each computational step (called the gas price).
If the transaction's intention is to invoke a method of a contract, it also contains input data, or if its intention is to deploy a contract, then it can contain the initialization code. The product of gas used and gas price is called transaction fees. To send ether or to execute a contract method, you need to broadcast...