What is Apache Solr?
Apache Solr is an Open Source enterprise search server based on the Lucene Java library. Features of Apache Solr include XML / HTTP and JSON APIs, hit highlighting, faceted search, caching, replication, a web administration interface, and much more.
There are many integrations of the Apache Solr Server for different applications, such as webcontentmanagement systems such as Drupal, TYPO3 and Wordpress. You can find the details about the TYPO3 extension on this page.