mysql client(s)

[Dick Hoogendijk]

PhpMyAdmin shows:

     Server: Localhost via UNIX socket
     Server version: 5.5.15
     Protocol version: 10
     User: root at localhost
     MySQL charset: UTF-8 Unicode (utf8)

Apache/2.2.19 (FreeBSD) mod_ssl/2.2.19 OpenSSL/0.9.8q DAV/2 PHP/5.3.6 
with Suhosin-Patch
MySQL client version: mysqlnd 5.0.8-dev - 20102224 - $Revision: 308673 $

I don't understand the client version thing. I have mysql-client-5.5.15 
installed too.
*Why* does PhpMyAdmin not show this client but an (to me) unknown 
program (mysqlnd-5.0.8-dev) Where does this program come from. I have no 
idea how it came on my system.