In the build instructions for OpenSSL it gives the options of running:

vcvarsall.bat with x86, x86_amd64, x86_arm, x86_arm64, amd64, amd64_x86;

x86_arm = arm 32-bit;
x64_arm64 = arm 64-bit;

amd64_x86 = 32-bit amd???
amd64 = 64-bit amd?

x86 = x86 32-bit;
x86_amd64 = x64 64-bit;

Why is x86 in AMD and why is AMD in x86, this is so confusing? I know there are plenty of questions about this sort of thing already on the internet, but I can’t find what I’m looking for, specifically the difference between x86_amd64 and amd64_x86.