  We review the main results that have been obtained in quantum cosmology from
the perspective of the de Broglie-Bohm quantum theory. As it is a dynamical
theory of assumed objectively real trajectories in the configuration space of
the physical system under investigation, this quantum theory is not essentially
probabilistic and dispenses the collapse postulate, turning it suitable to be
applied to cosmology. In the framework of minisuperspace models, we show how
quantum cosmological effects in the de-Broglie-Bohm's approach can avoid the
initial singularity, and isotropize the Universe. We then extend minisuperspace
in order to include linear cosmological perturbations. We present the main
equations which govern the dynamics of quantum cosmological perturbations
evolving in non-singular quantum cosmological backgrounds, and calculate some
of their observational consequences. These results are not known how to be
obtained in other approaches to quantum theory. In the general case of full
superspace, we enumerate the possible structures of quantum space and time that
emerge from the de Broglie-Bohm picture. Finally, we compare some of the
results coming from the de Broglie-Bohm theory with other approaches, and
discuss the physical reasons for some discrepancies that occur.
