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What is a node ?

This module will guide you through the complete installation and setup of your own Tezos node on various operating systems.

In this chapter, the reader will also grasp what a node is and how important it is in a Blockchain network.

What is a node?

The node is the main actor of the Tezos blockchain and has two main functions: running the gossip network and updating the context.
The gossip network is where all Tezos nodes exchange blocks and operations (see the Admin Client to monitor P2P connections). On this peer-to-peer network, an operation is spreading through the network and then baked into a block.
The shell receives blocks from the gossip network and uses them to keep the current context up to date: A full state of the blockchain shared by all peers. Approximately every 15 seconds, a new block is created. When the shell receives it, it applies each operation to its current context and computes a new context.

The last block received on a chain is also called the "head" of that chain. Each new head is then advertised by the node to its peers, disseminating this information to build a consensus across the network.

Other than passively observing the network, your node can inject its own new operations when instructed by the octez-client application and even register as a delegate to bake new blocks with the octez-baker- prefix. The node also has a view of the multiple chains that may exist concurrently and selects the best one based on its fitness (see Liquid Proof-of-Stake chapter in Tezos Basics module).