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

they are different

IA-64 is itanium - an architecture for servers

x64 is what 64bit intel core and amd cpus implement