Anything related to Lucene indexes: querying, configuring, maintaining, ...
Lucene is an open-source search engine used in Sitecore CMS for indexing and searching the contents of a Web site. Sitecore implements a wrapper for the Lucene engine which has its own API. Sitecore supports three different search engines: Solr, Azure Search, and Lucene till Sitecore version 9.2. The Lucene search engine will be deprecated in a later release(9.3 onwards), and Sitecore recommend that you no longer use this search engine.
Questions related to Solr or Azure Search should be tackled with corresponding tags - solr or azure-search
