  Launched on 12 Aug. 2018, NASA's Parker Solar Probe had completed 13 of its
scheduled 24 orbits around the Sun by Nov. 2022. The mission's primary science
goal is to determine the structure and dynamics of the Sun's coronal magnetic
field, understand how the solar corona and wind are heated and accelerated, and
determine what processes accelerate energetic particles. Parker Solar Probe
returned a treasure trove of science data that far exceeded quality,
significance, and quantity expectations, leading to a significant number of
discoveries reported in nearly 700 peer-reviewed publications. The first four
years of the 7-year primary mission duration have been mostly during solar
minimum conditions with few major solar events. Starting with orbit 8 (i.e., 28
Apr. 2021), Parker flew through the magnetically dominated corona, i.e.,
sub-Alfv\'enic solar wind, which is one of the mission's primary objectives. In
this paper, we present an overview of the scientific advances made mainly
during the first four years of the Parker Solar Probe mission, which go well
beyond the three science objectives that are: (1) Trace the flow of energy that
heats and accelerates the solar corona and solar wind; (2) Determine the
structure and dynamics of the plasma and magnetic fields at the sources of the
solar wind; and (3) Explore mechanisms that accelerate and transport energetic
particles.
