What is the difference between x64 and IA-64?

Question

I was on Microsoft\'s website and noticed two different installers, one for x64 and one for IA-64. Reference:Installing the .NET Framework 4.5, 4.5.1

My understandin

Answer 1

x64 is short for x86-64 which is an extension of the x86 instruction set.

IA-64 is for the Itanium 64 bit Architecture (by Intel)