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Low mass cores are the simplest sites where solar-type
stars are born, and their study offers the best opportunity to
determine observationally the initial conditions of star formation.
Thanks to an intense effort in observations and modeling
during the past several years, a number of issues on the physical and
chemical structure of cores have been clarified, and a reasonable
consensus view on some of the internal properties of cores has
emerged. Cores are now understood to have flattened, quasi Bonnor-Ebert
density profiles, centrally depressed temperature gradients, subsonic
internal motions, and chemical inhomogeneities resulting from the
depletion of most molecular species, in particular CO, at the
high densities typical of their interior. Despite this significant
progress, a number of important questions on core physics remain open,
in particular concerning the formation mechanism, equilibrium state,
and eventual collapse to form stars. In this talk, I will review some
of our current understanding of core properties and I will discuss new
observations and studies aimed to clarify the questions that remain
unanswered.
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