Not Logged in session question

I'm trying to find a way to keep sessions live for shoppers that are not logged in. What's the difference between setting the configure.php from "database" to "File" in the sections below. What effect would that code edit have, if any?

  define('USE_PCONNECT', 'false'); // use persistent connections?
  define('STORE_SESSIONS', 'db'); // use 'db' for best support, or '' for file-based storage

  // The next 2 "defines" are for SQL cache support.
  // For SQL_CACHE_METHOD, you can select from:  none, database, or file
  // If you choose "file", then you need to set the DIR_FS_SQL_CACHE to a directory where your apache 
  // or webserver user has write privileges (chmod 666 or 777). We recommend using the "cache" folder inside the Zen Cart folder
  // ie: /path/to/your/webspace/public_html/zen/cache   -- leave no trailing slash  
  define('SQL_CACHE_METHOD', 'database'); CHANGE THIS TO FILE
  define('DIR_FS_SQL_CACHE', '/home/stones/public_html/cache');