x64(X86-based 64-bit) The current computer architecture from Intel and AMD. Also called "x86-64," modern x86-based laptop and desktop computers have 64-bit CPUs rather than 32 bits. The x64 generally refers to the hardware, not the operating system. See 64-bit computing.
Intel 64 and AMD64
The official designations of 64-bit chips from Intel and AMD are Intel 64 and AMD64 respectively. See Intel 64, AMD64, x64 Edition and x86.