  The ALICE apparatus includes an Inner Tracking System for high-precision
vertexing and tracking at midrapidity. Thanks to this detector, remarkable
results were obtained with Run 2 data in all collision systems studied at the
LHC. In this contribution, the role of the ITS in the event, track and
secondary vertex reconstruction is highlighted, and the comparison of the
resolution on the track impact parameter to the collision point in data and
Monte Carlo simulations is reported. Finally, some of the main physics results
obtained in pp and Pb--Pb collisions relying on the excellent ALICE vertexing
and tracking capabilities are presented.
