Pdo Or Mysqli

Hello,

I was just wondering, but has anyone noticed that we can have 2 different types of MySQL:

1. MySQLi

2. PDO

Can anyone explain to me what the difference is and what the performance is between these two, because the only link I found was this one: http://wooptoo.com/blog/pdo-vs-mysqli-performance-comparison/

PHP PDO supports 12 database drivers in comparison with MySQLi which supports only MySQL. MySQLi insignificantly faster than PDO.