  I review both well established and more recent findings on the properties of
bars, and their host galaxies, stemming from photometric and spectroscopic
observations, and discuss how these findings can be understood in terms of a
global picture of the formation and evolution of bars, keeping a connection
with theoretical developments. In particular, I show the results of a detailed
structural analysis of ~ 300 barred galaxies in the Sloan Digital Sky Survey,
providing physical quantities, such as bar length, ellipticity and boxyness,
and bar-to-total luminosity ratio, that can either be used as a solid basis on
which realistic models can be built, or be compared against more fundamental
theoretical results. I also show correlations that indicate that bars grow
longer, thinner and stronger with dynamical age, and that the growth of bars
and bulges is connected. Finally, I briefly discuss open questions and possible
directions for future research.
