Endpoint Protection

Release Updates (RUx) typically contain a significant number of fixes and may include feature-work or enhancements.  The current Release Update is considered the latest release of the product and is the appropriate version for most customers performing a new install or upgrading from an earlier release or build of the product.

 

Maintenance Patches (RUx MPx) contain a small number of fixes for specific customer issues and are based on a specific RU.  MPs can only be applied against the specific Release Update upon which they are based, e.g., RU6 MP1 can only be applied against RU6.  Maintenance Patches are appropriate for customers experiencing an issue that is resolved in the Maintenance Patch.

RTM - Release To Manufacturing

MR - Maintenance Release (Now replaced by the term "RU")

RU - Release Update

MP - Maintenance Patch

PP - Point Patch

For detailed Release Notes that document the customer fixes included in a particular release, or for other technical product info, please see the SEP landing page at Symantec Support at:http://www.symantec.com/business/support/overview.jsp?pid=54619

For more understanding, check these Articles : 

General supported migration paths for Symantec Endpoint Protection Manager (SEPM) / Symantec Endpoint Protection (SEP) - Terminology used in acronyms

What are the officially released versions of Symantec Endpoint Protection (SEP)?