i386 is just one the first model in the x86 familly of processors, and instructions sets.
For more informations, you might want to take a look at :
- Intel 80386
- x86
Quoting the second page :
The term x86 refers to a family of
instruction set architectures[1] based
on the Intel 8086. The term is derived
from the fact that many early
processors that are backward
compatible with the 8086 also had
names ending in “86”.
And, quoting the first one :
The Intel 80386, also known as the
i386, or just 386,[1] was a 32-bit
microprocessor introduced by Intel in
1985. […]
As the original implementation of the 32-bit
extensions to the 8086 architecture,
the 80386 instruction set, programming
model, and binary encodings are still
the common denominator for all 32-bit
x86 processors.
This is termed
x86, IA-32, or the i386-architecture,
depending on context.