This document provides an overview of Elasticsearch, including its key features and common use cases. It begins with an introduction to full text search and how Elasticsearch works. It then covers basic concepts in Elasticsearch like indexes, types, mappings, and scoring. Next, it lists some common users of Elasticsearch. Following that are examples of real world use cases for Elasticsearch like searching different data types, geolocation searching, and centralized logging. The document concludes by mentioning some Elasticsearch plugins and related products like Logstash, Kibana, Watcher, and Shield.