ElasticSearch Basic Concepts

- Cluster:- A cluster is a collection of one or more nodes that together hold the entire data. It provides distributed indexing, high availability and search capabilities across all nodes.
- Node:- A node is a single server in a cluster, which stores data and participates in the cluster’s indexing and search capabilities.

Index:- An index is a collection of documents and is identified by a name. you can consider it as a database in RDBMS. we have to use the index name while performing indexing, search, update and delete operations against the documents in it.
Type:- A type is nothing but the type of a document. You can consider it as a table in RDBMS. you can define multiple types in your index.
Document:- A document is a basic unit of information that can be indexed. It is stored in JSON format which is a global internet data interchange format.
Shards:- Elasticsearch facilitates High availability, fault tolerance, scalability by providing the ability to subdivide the index into multiple pieces called shards. Each shard can be hosted on any node within the cluster. We can set a number of shards manually inside index schema for a particular Index.
Replicas:- Elasticsearch allows you to make one or more copies of your index’s shards called replica shards or replica. We can set a number of replicas manually inside index schema for a particular Index.

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