Information about the content of your website is stored in an index file. The index files are located in ~/App_Data/CMSModules/SmartSearch/{Index code name} within your website's folder.
Documents and forums in Kentico CMS are reflected in the index file as index documents. The data structure of the index documents is much more suitable for being searched through, resulting in significantly higher search performance compared to linear SQL search.
The index documents may contain fields that the corresponding Kentico CMS documents contain, based on the settings made on each document type's Search fields tab. Depending on the settings, a document within the index file gets created by the Index writer when a new document is created in the system. The Index searcher, on the other hand, searches through the index file and returns the relevant results from it.
Brief example
Let's take the following model scenario to explain the life cycle of a document in the index file:
1. A new document is created and stored in the database. When the fields to be indexed are defined for the document type, a new indexing task is logged in the database on the document's creation.
2. The Smart search checks the database automatically on a regular basis for presence of indexing tasks.
3. When the Smart search module finds the task, it processes it and the new page gets indexed.
4. Now a user comes to the site and sends a search request via some Smart search web part.
5. The request gets passed to the Smart search module.
6. It modifies the request into a searchable form, searches the index and returns results based on what was found in the index.
Page url: http://devnet.kentico.com/docs/devguide/index.html?smart_search_how_it_works.htm