The meaning of i386 and AMD64

First, you can simplify a concept, I386=intel 80386. In fact, i386 is commonly used as a generic term for Intel (Intel) 32-bit microprocessors.
  On the installation disk of the Windows NT class system, usually i386 is a folder on its root, which contains the basic installation information required by the hardware.
  The installation folder for Windows2000 and Windows XP is i386, which can normally be found under the installation CD. To speed up installation, the Setup program copies i386 to the hard disk before installing. This folder can also be used to install drivers when the system changes in the future (add or subtract new hardware), or to increase the service components and software included with the system.
  In other places where processor instructions are involved, it is often possible to use the term i386, which is similar to PPC as a Power PC microprocessor abbreviation.

AMD64, also known as "x86-64" or "x64", is a 64-bit computer processor architecture. It is built on the existing 32-bit x86 architecture, developed by AMD, with its own products in the AMD64 instruction set Athlon 64, Athlon FX, Athlon X2, Turion 64, Opteron and the latest Sempron processors.

The meaning of i386 and AMD64