PDO php in drupal

When i was reading about connection to dB in drupal, i come across a lot of unsual & unfamiliar connection method in drupal that has something to do with PDO. So ichecked in php.net & google it. So, this is what i found; PDO is one of php techniques in connecting to database regardless of its type (MySql, Oracle, Postgress). Anyway there is not much doc about it in php.net. there are few references in other links though as follows:

1. http://www.kitebird.com/articles/php-pdo.html
   
2. http://www.phpro.org/tutorials/
   
3. http://developers.sun.com/