i386 is one of the SupportedArchitectures. It is the original 32 bit x86 architecture.
Most desktop systems today are 64 bit systems and use the amd64 architecture. In the past most desktop systems were compatible with the Intel 386 (i386) architecture; this remains true for 32 bit systems.
Many assembly coders whine and rant about the i386. The i386 seems to have more than its fair share of quirks.