  In this review we consider in detail different theoretical topics associated
with interaction in the dark sector. We study linear and nonlinear interactions
which depend on the dark matter and dark energy densities. We consider a number
of different models (including the holographic dark energy and dark energy in a
fractal universe) with interacting dark energy (DE) and dark matter (DM), have
done a thorough analysis of these models. The main task of this review was not
only to give an idea about the modern set of different models of dark energy,
but to show how much can be diverse dynamics of the universe in these models.
We find that the dynamics of a Universe that contains interaction in the dark
sector can differ significantly from the Standard Cosmological Model (SCM).
