The officer kept my license and gave me a 30 day permit. What does that mean?

It means the officer will submit a sworn report to the DMV requesting your license be administratively suspended for one year.  You have thirty days after your arrest to file an appeal of this report.  If you do not do so within thirty days your license will be suspended on the 46th day after your arrest.  Filing an appeal could postpone a license suspension or keep one from occurring altogether.  This hearing is completely separate from any criminal hearing and its purpose is to determine whether or not your license will be suspended.  It does not in any way decide your guilt or innocence for DUI.