Solr Search Engine is a search engine optimization framework on the top of Apache license index. For huge applications who are dealing with huge amount of data, search will becomes slow to pick the data from database for different search criteria.
Top Search Applications like Google, yahoo, Bing they will implement internally using solr search engine. Solr Search is a textual based search which will pick the data from database and will store in the form of indexes in the file system.
Daily at one time when the web application is not having huge traffic admin team will run the solar search scripts which will pick the data from DB logically and create indexes in the file system.
If anybody searches the application they will get the results from indexes and will be 20 times faster than as getting the data from the database.
There were various types of search analyzer will be available like Standard analyzer which will do keyword search as we as auto suggestion search etc.