Hello,
You are almost correct. Let me get that corrected.
Symantec Trusted are the Symantec signed Files, whereas Community Trusted are the files which are Symantec and Norton signed, Microsoft Catalog Signed, or Authenticode Signed.
and other files are based on Reputation:
How Symantec Endpoint Protection uses reputation data to make decisions about files
http://www.symantec.com/docs/HOWTO55275
To know more check this Whitepaper on Symantec Insight on
https://www-secure.symantec.com/connect/downloads/insight-deployment-best-practices-whitepaper
Incase, you want to check the Symantec Download Insight, check this Video:
https://www-secure.symantec.com/connect/videos/symantec-download-insight-symantec-endpoint-protection-121
Hope that helps!!