The native Assembly language of the given platform.

For example it would be stupid to write anything in Motorola 68000 Assembly for Intel x86 platform: it wouldn't work.

No. Each assembly language is based on either a processor family or a specific computer.

Different. Each assembly language is based on a series of processors or specific machines.

"The x86 architecture first appeared as the Intel 8086 CPU released in 1978, a fully 16-bit design based on the earlier Intel 8085. Although not binary compatible, it was designed to allow assembly language programs written for the 8085 to be mechanically translated into the equivalent 8086 assembly. " Here's the entire Article: http://en.wikipedia.org/wiki/X86

The X86 64 is considered to refer to the central processing unit for computers. The X86 64 predominantly supports both physical and virtual memory on computer systems.

Machine languages are composed of instructions intended to be read directly by the microprocessor (the computer's CPU). The manufacturer of the CPU determines it's "INSTRUCTION SET"

ASSEMBLY LANGUAGE on the other hand IS NOT machine dependent. The same commands ADD, Divide, Move, etc are universal. HOWEVER the ASSEMBLY LANGUAGE has to have an INTERPRETER for EACH CPU, and that will translate the Universal ASSEMBLY language to the MACHINE SPECIFIC code required to program the CPU.