Find information quickly
Elasticsearch builds a searchable index of information, much like the index at the back of a book. A shop might use it to help customers find products; a team might use it to investigate application logs, which record what software has done. It can run on the team’s servers or through a hosted service.
Elastic is the company behind Elasticsearch. The Elastic Stack includes related tools such as Kibana, used to explore the data. ELK Stack is an older name based on Elasticsearch, Logstash, and Kibana.
How OpenSearch fits in
OpenSearch grew out of Elasticsearch, but they are now separate products. Amazon OpenSearch Service is AWS’s service for running OpenSearch and certain older Elasticsearch versions.