Lucene is an open source project that provides text search engine libraries. It is widely adopted for many search engine technologies. It has strong community contributions, which makes it much stronger as a technology backend. Lucene is a simple code library that you can use to write your own code by using the API available for searching, indexing, and much more.

For Lucene, a document consists of a collection of fields; they are name-value pairs consisting of either text or numbers. Lucene can be configured as a text analyzer that tokenizes a field’s text to a series of words. It can also do further processing, such as substituting with synonyms or other similar processes. Lucene stores its index on the disk of the server, which consists of indexing for each of the documents. The index is an inverted index that stores the mapping of a field to its relevant document, along with the position of the word from the text of the document. Once you have the index in place, you can search for documents with the input of a query string that is parsed accordingly to Lucence. Lucene manages to score a value for each of the relevant documents and the ones that are high-scoring documents are displayed.