For more information, please see About Lists of Windows Server Packages Updated After the Release of Windows Server 2008 R2 Service Pack 1 (SP1).
Pronichkin edited Original. Comment: Fixed Wiki links
What is the meaning of GDR and LDR?
Basically, GDR and LDR (previously known as “QFE”) are so called “Service Branches”. GDR stands for “General Distribution Release” and LDR stands for “Limited Distribution Release”.
Speaking the words of Microsoft Support Knowledge Base, “GDR service branches contain only those fixes that are widely released to address widespread, critical issues. LDR service branches contain hotfixes in addition to widely released fixes”.
If that does not make things clear I could write a Wiki article on this stuff. Please let me know what you think.