  We find the eigenvalues $E_{\alpha} $ and eigenvectors $|E_{\alpha}>$ of the
extended Hubbard dimer and we represent each part $E_{\alpha} |E_{\alpha}> <
E_{\alpha} |$ of the dimer Hamiltonian $(\alpha =1,2,...,16)$in the second
quantizations with the use of the Hubbard and spin operators. This procedure
gives a review of all competitive, intrinsic interactions, deeply hidden in the
orginal form of the considered Hamiltonian. Among competitive interactions we
can find ferromagnetic and antiferromagnetic interactions (also in the form
appearing in the $t-J$ model), hopping of the Cooper pairs between different
dimer lattice sites (similar as in Kulik-Pedan, Penson-Kolb models), as well
as, intersite Cooper pair interactions. We plot several coupling constants of
these interactions vs Coulomb intrasite interaction $U$ to show that the
competition between them strongly depends on the model parameters. The
thermodynamical activity of each particular interaction, belonging to a given
energy level, depends, however, on the occupation of this level. From the
presented review of interactions it is evident that the extended Hubbard model
is capable to describe the properties of superconductors with magnetic ordering
(including also high-$T_C$ superconductors) where a strong competition between
magnetism and superconductivity takes place.
