BCP "native mode" exports data in binary form, which is generally more compact than the "character mode" which translates each data value into human-readable form.
Native mode output is best used only on the same platform (OS + hardware architecture) as the native binary encoding of values can differ based on the platform. The most obvious example being the difference between big-endian and little-endian hardware architectures.
, where you have the difference of an integer value of 1 being stored as either 0x00000001 or 0x01000000.