Manual:$wgSQLiteDataDir/en

Details
To override default SQLite data directory.

By default it is "data" directory in the parent of the document root (i.e. the folder where the web server stores web documents).

SQLite stores each database in its own file. So MediaWiki must give it the directory and filename, to get access to the database. This also applies to humans trying to access the database on the terminal (see Manual:SQLite).

This variable allows for storing the database outside the document root, because, in most cases, one does not want to give access to the database file through the web.