  The electronic nematic responses in Fe-based superconductors have been
observed ubiquitously in various experimental probes. One novel nematic
character is the d-wave {\it bond} orbital-relevant nematic charge order which
was firstly proposed by symmetry analysis and then conformed by angle-resolved
photoemission spectroscopy. In this paper, we present a mechanism that the
driving force of the orbital-relevant nematic charge order is the reduction of
the large Hubbard energy in the particle-hole charge channel by virtual hopping
processes. This is one scenario from strong-coupling consideration. The same
virtual hopping processes can lead to a super-exchange interaction for the spin
magnetic order in the particle-hole spin channel and a pairing interaction for
the superconducting order in the particle-particle channel. Thus the electronic
nematic order, the spin magnetic order and the pairing superconducting order
are intrinsically entangled and they can all stem from the same microscopic
virtual hopping processes in reduction of the Hubbard energy. The electronic
nematicity, the spin magnetism and the pairing superconductivity in
unconventional superconductors are proposed to be unified within this
mechanism.
