The document discusses using Elasticsearch for full-text search and analytics. It introduces Elasticsearch and how it compares to relational databases. It covers installing and interacting with Elasticsearch via its RESTful API, including indexing, retrieving, updating and deleting documents. The document explains Elasticsearch's architecture including clusters, nodes, shards, indexes, types and documents. It demonstrates querying Elasticsearch using its query domain specific language. Finally, it presents a case study of building a restaurant search engine with Symfony and Elasticsearch.