In particular, the execution of smart contracts is an example of a transaction. For example, if A tries to send 100 ether to B but A has 0 ethers and a block includes this transaction, the full nodes will realize this does not follow the rules of Ethereum and reject that block as invalid. Transactions and blocks that do not follow the rules are not used to determine the current state of the Ethereum network. They maintain the current state of the network (as defined according to the Ethereum specifications). That is, they ensure that the transactions contained in the blocks (and the blocks themselves) follow the rules defined in the Ethereum specifications. Full nodes verify block that is broadcast onto the network. In general, we can divide node software into two types: full nodes and light(weight) nodes. RPC is usually implemented in the form of web APIs (HTTP) or Unix sockets. Some node software also allows other programs to indirectly interact with the blockchain this is provided through some remote procedure call (RPC) facility.
This software mostly, if not always, also provides wallet functionality (software that allows users to perform transactions on the blockchain). Software that can act as an Ethereum node include Parity and Go-ethereum ( geth). A node is a device/program that communicates with the Ethereum network.
