I am always confused by the difference between i386 and amd64 when I try to download some packages for my ubuntu. This has been the second time that I Google for the difference between them. I think I should take a little note on the subject.
Differences
From stackoverflow, i386 edition can be simply treated as 32-bit edition and amd64 as 64-bit.
Historical Reason
The reason for the weird divergence of the naming of instruction sets is that the two instruction sets are first launched by different vendor. i386 was introduced by Intel in 1985 and amd64 was launched by AMD in 2003 (originaly named x86-64).
Other names
x86-64: x64, x86_64, amd64, Intel 64
i386: Intel 80386, 386,