You store a copy of all your data in Elasticsearch that you want to be able to search for. It comes with a very powerful and customizable built-in search algorithm so you don't have to write one on your own, and you interact with it via a built-in REST API. That's the 10,000 foot view!

ElasticSearch is another data storage engine, like the Postgres, MySQL, CSV, JSON documents, and anything else you know about. ElasticSearch is based on Lucene Information Retrieval System core.

When to use ElasticSearch:

1. You need full text search on your data
2. Sort, Search, Rank search results
3. Data is unstructured organised into self-contained documents.

Some of the advantages:

1. Speed and accuracy
2. Data need not be atomic or referential
3. Schema free data storage
4. Easy to use REST API
5. JSON like query language