Probably, you are referring to the possibility to use a SDXC card as a Time Machine drive. It's possible to do it, but I highly recommend you to use an external drive, because the card will get full quickly, and Time Machine deletes old backups when the disk gets full.
The steps to set up a SDXC card as the Time Machine disk are the same as for an external disk > http://support.apple.com/kb/HT1427?viewlocale=en_US
If you have any questions about Time Machine, check the Pondini's page > http://pondini.org
Thanks for the quick reply! I do not store anything in my Mac Mini, in fact I do not even use email nor web browse. It is strictly used as a media server for itunes so the only thing I would like to back up would be all the settings in case I ever need to restore from back up I would not have to re-enter all my settings again.