One name is the name generated by the build lab:
7600: build #
16385 (0x4001): QFE #
090713-1255: build tag
x64: compiled for x86-64
fre: "free" build (vs. "checked" builds that have compiler optimizations turned off and debugging information left in; checked builds of Windows are typically used only by the Windows Team or by MSDN subscribers who need to do OS-level debugging; TechNet does not get checked builds)
client: component identifier (vs. WDK, SDK, etc.)
GRMCULXFRER_EN: disc label
DVD: disc type (duh!)
That's the "original" name, and that's the sort of name that gets used in most official non-retail distribution channels (e.g., Connect), and, as I understand it, that's the name that all the employees see. Also, for things like the WDK, SDK, and WAIK, when you download it from the official download center, they will have similar "build lab" file names.
The exception to all this is MSDN/Expression/TechNet, where they use what amounts to a packaging name. The "X15-65921" is actually a part number that gets printed on the pressed discs and, as I understand it, is used for things like inventory and ordering.