x86, x86-64, i386, IA32, IA64...

 x86：Intel从16位微处理器8086开始的整个CPU芯片系列，系列中的每种型号都保持与以前的各种型号兼容，主要有8086，8088（前面两个是16位CPU），80186，80286（这两个是过渡产品）， 80386，80486以及以后各种型号的Pentium芯片[奔腾，P2, P4，赛扬...]（这些都是32位CPU）

x86-64：如下是维基百科上的解释，大致翻译一下，x86-64是x86指令集的超集，在x86处理器上可以运行的程序可以运行在x86-64上（这也是为啥现在买的一些64bits CPU可以直接运行Win XP的原因）。x86-64是AMD发明的，也叫AMD64，Intel克隆了一把，叫做Intel 64，也叫EM64T。

x86-64 is a 64-bit superset of the x86 instruction set architecture. Because the x86-64 instruction set is a superset of the x86 instruction set, all instructions in the x86 instruction set can be executed by central processing units (CPUs) that implement the x86-64 instruction set; therefore these CPUs can natively run programs that run on x86 processors from Intel, Advanced Micro Devices (AMD), and other vendors.

x86-64 was designed by AMD, who have since renamed it AMD64. It has been cloned by Intel under the name Intel 64 (formerly known as EM64T among other names).[1] This leads to the common use of the names x86-64 or x64 as more vendor-neutral terms to collectively refer to the two nearly identical implementations.
x86和x86-64可以认为就是一种特定的指令集

i386：也是维基上的解释，也就是指Intel 80386，是第一个32位的x86架构的处理器，用了20多年了，后面出的 486（80486，i486），586（80586，Pentium，P5），686（80686，Pentium Pro，P6）等等都与之兼容。

The Intel 80386, otherwise known as the Intel386, i386 or just 386, is a microprocessor which has been used as the central processing unit (CPU) of many personal computers and workstations since 1986. It was the first x86 processor to have a 32-bit architecture, with a basic programming model that has remained virtually unchanged for over twenty years and remains completely backward compatible.

IA32：可以认为就是x86或者x86-32，也是一个指令集。

IA-32 (Intel Architecture, 32-bit), often generically called x86 or x86-32, is the instruction set architecture of Intel's most commercially successful microprocessors. It is a 32-bit extension, first implemented in the Intel 80386, of the earlier 16-bit Intel 8086, 80186 and 80286 processors and the common denominator for all subsequent x86 designs. This architecture defines the instruction set for the family of microprocessors installed in the vast majority of personal computers in the world.

IA64：就是所谓的安腾，Intel跟HP联合折腾的一种64-bits全新架构，与x86系列不兼容，它放弃了以前的x86架构，认为它严重阻碍了处理器的性能提高。由于它不能很好地解决与以前32位应用程序的兼容，所以应用受到较大的限制，尽管目前Intel采取了各种软、硬方法来弥补这一不足，但随着AMD Operon处理器的全面投入，Intel的IA－64架构的这两款处理器前景不容乐观。
Itanium is the brand name for 64-bit Intel microprocessors that implement the Intel Itanium architecture (formerly called IA-64). Intel has released two processor families using the brand: the original Itanium and the Itanium 2. Starting November 1, 2007, new members of the second family are again called Itanium. The processors are marketed for use in enterprise servers and high-performance computing systems. The architecture originated at Hewlett-Packard (HP) and was later developed by HP and Intel together.