  The Ariel mission will characterise the chemical and thermal properties of
the atmospheres of about a thousand exoplanets transiting their host star(s).
The observation of such a large sample of planets will allow to deepen our
understanding of planetary and atmospheric formation at the early stages,
providing a truly representative picture of the chemical nature of exoplanets,
and relating this directly to the type and chemical environment of the host
star. Hence, the accurate and precise determination of the host star
fundamental properties is essential to Ariel for drawing a comprehensive
picture of the underlying essence of these planetary systems. We present here a
structured approach for the characterisation of Ariel stars that accounts for
the concepts of homogeneity and coherence among a large set of stellar
parameters. We present here the studies and benchmark analyses we have been
performing to determine robust stellar fundamental parameters, elemental
abundances, activity indices, and stellar ages. In particular, we present
results for the homogeneous estimation of the activity indices S and log(R'HK),
and preliminary results for elemental abundances of Na, Al, Mg, Si, C, N. In
addition, we analyse the variation of a planetary spectrum, obtained with
Ariel, as a function of the uncertainty on the stellar effective temperature.
Finally, we present our observational campaign for precisely and homogeneously
characterising all Ariel stars in order to perform a meaningful choice of final
targets before the mission launch.
