The Premium version is actually the standard PRO version from the official website of the developers. Besides free options, the PRO version, costs money and it's on per year/month subscription, but it also provides additional support for virus and trojan identification, website traffic blocking system, email scanning and malware cloud testing along with unlimited tech support 24/7.
For more information, you can access the comparison page provided by the developers: http://www.avira.com/en/avira-antivirus-pro
Scroll down and click the Compare button to see exactly.