Amazon Elasticsearch Service contains the following components:
Domain: An Amazon Elasticsearch domain comprises an Elasticsearch cluster – hardware and software – along with additional hardware and software providing load-balancing, security, and monitoring. The domain is exposed by service endpoints for Amazon Elasticsearch Service.
Cluster: A cluster is a collection of one or more data nodes, optional dedicated master nodes, and storage required to run Elasticsearch.
Node: A node is single instance within an Elasticsearch cluster that has the ability to recognize and process or forward messages to other nodes.
Storage: Amazon Elasticsearch Service supports two distinct storage types, the Instance (default) storage or Elastic Block Store (EBS) – general purpose (SSD), provisioned IOPS (SSD), and magnetic.