Can you tell me the detailed difference between PDO and Mysql_connect?

Dear PHP Officer, From China. I have heard of PDO extension for more than one year, but I havn't test the difference between PDO and Mysql_connect. I search a very long time for other programers' test report from google, but failed. There isn't any wholeside report of it. Only anyone said that PDO has a more efficiency when high concurrent. I have no idea about more detail of PDO. Can you give me a list about it? I mean, I want a roughly list, describing what efficiency is about PDO when compare with Mysql? Sorry for my poor English. and wait for your reply. Your Sincely...... Steven. 21/04/2011