The Pierre Auger Observatory: Results and open issues

We will present the status and the main results of the Pierre Auger Observatory. These include the measurement of the cosmic ray energy spectrum above 1018 eV, where we observe a suppression for energies larger than 5.5×1019 eV, the analyses of the arrival directions and the chemical composition. The implications on the origin and on the acceleration mechanisms of the most energetic cosmic rays will be discussed with a particular emphasis to the still open issues.