Linux User : What is i386, i586, i686

I just found out that linux has so many version Hardware than windows.
Windows only have 2 kind version of Hardware, which is x86 (32 bit) or x64 (64 bit).
Linux has 3 version of hardware, and that are i386, i586, and i686.
the differences are :

kernel i686 -> Pentium Pro/Celeron/Pentium II/Pentium III/Pentium IV
kernel i586 -> Pentium-Classic
kernel i386 -> 386/486

linux user can check what kind version of your hardware by type this command :
#cat /proc/cpuinfo ( check your model name )


the sources that i quote from : http://www.linuxquestions.org/questions/linux-hardware-18/what-is-the-meaning-of-i386-i686-and-where-i-can-find-this-information-327233/