Because it has been released on the 50th week of 2007 (that makes the 2007.50 part.
So as far as I know:

RX-34_2008SE_2.2007.50-2_PR_COMBINED_MR0_ARM.bin

RX-34 is the N800 tablet (RX-44 the N810).
2008SE is the OS edition
_2 is the release version (_1 was the Beta)
2007.50 is the week it was released
-2 should be some internal versioning about the package
_PR_COMBINED_MR0 should be related to the hardware arch
_ARM is the processor architecture
.bin because it's in binary format.