  The recent GAIA DR2 measurements of distances to galactic novae have allowed
to re-analyse some properties of nova populations in the Milky Way and in
external galaxies on new and more solid empirical bases. In some cases we have
been able to confirm results previously obtained, such as the concept of nova
populations into two classes of objects, that is \emph{disk} and \emph{bulge}
novae and their link with the Tololo spectroscopic classification in \emph{Fe
II} and \emph{He/N} novae. The recent and robust estimates of nova rates in the
Magellanic Clouds galaxies provided by the OGLE team have confirmed the
dependence of the normalized nova rate (i.e., the nova rate per unit of
luminosity of the host galaxy) with the colors and/or class of luminosity of
the parent galaxies. The nova rates in the Milky Way and in external galaxies
have been collected from literature and critically discussed. They are the
necessary ingredient to asses the contribution of novae to the nucleosynthesis
of the respective host galaxies, particularly to explain the origin of the
overabundance of lithium observed in young stellar populations. A direct
comparison between distances obtained via GAIA DR2 and Maximum Magnitude vs.\
Rate of Decline (MMRD) relationship points out that the MMRD can provide
distances with an uncertainty better than 30\%. Multiwavelength observations of
novae along the whole electromagnetic spectrum, from radio to gamma-rays, have
revealed that novae undergo a complex evolution characterized by several
emission phases and a non-spherical geometry for the nova ejecta.
