  The Pierre Auger Observatory is a unique facility designed to study
ultra-high energy cosmic rays, with energies up to 10$^{20}$ eV and beyond. The
Observatory is located in Argentina and comprises more than 1600 water
Cherenkov detectors spread over an area of 3000 square kilometers overlooked by
Fluorescence detectors. The first phase of the Observatory's data-taking began
in 2004 and continued until the end of 2021. In this contribution, the results
from the Phase~I data analysis of the Pierre Auger Observatory are presented.
They include, among others, measurements of the cosmic-ray energy spectrum,
composition, and arrival direction anisotropy. The Phase~I results from the
Pierre Auger Observatory provide major advances in the understanding of the
ultra-high energy cosmic ray phenomena and lay the foundation for second-phase
studies with the upgraded AugerPrime detector. The status of the AugerPrime
upgrade and its performance will be also discussed.
