Elasticsearch is a distributed system. It consists of multiple processes running across different machines in a network that communicate with the other processes. In Chapter 1, Introducing the Elastic Stack, we downloaded, installed, and started Elasticsearch. It started what is called a single node of Elasticsearch, or a single node Elasticsearch cluster.

An Elasticsearch node is a single server of Elasticsearch, which may be part of a larger cluster of nodes. It participates in indexing, searching, and performing other operations that are supported by Elasticsearch. Every Elasticsearch node is assigned a unique ID and name when it is started. A node can also be assigned a static name via the node.name parameter in the Elasticsearch configuration file, config/elasticsearch.yml.

At the lowest level, a node corresponds to one instance of the Elasticsearch process. It is responsible for managing its share of data.