Lucene is a Java full-text search engine. Lucene is not a complete application, but rather a code library and API that can easily be used to add search capabilities to applications.
This is the official documentation for Apache Lucene 4.5.1. Additional documentation is available in the Wiki.
The following section is intended as a "getting started" guide. It has three audiences: first-time users looking to install Apache Lucene in their application; developers looking to modify or base the applications they develop on Lucene; and developers looking to become involved in and contribute to the development of Lucene. The goal is to help you "get started". It does not go into great depth on some of the conceptual or inner details of Lucene: