Apache Solr is a REST server for indexing content. It's great in performance.
In this session we'll learn to integrate Solr with Drupal for making powerful searches and boosting the performace of a Drupal site because these searches don't impact the db.
There are two great modules: apachesolr and search_api. With each one we get different things. Let's know both of them and you will use the one that fits better your needs.