An overview will be given of PSI proton accelerator facility and its applications. To achieve a 590 MeV proton beam at the very high beam intensities of 2.4 mA CW, it requires dedicated measures in the acceleration process, in the beam transport systems and in the targets. After a general introduction of several basic cyclotron operation principles, some high-intensity effects in beam dynamics will be discussed, followed by an overview of measures taken to accelerate, extract and transport such high beam intensities. Several examples will be shown on how highly radioactive components are being handled. The high-intensity proton beams are used to produce muon and neutron beams for various physics and industrial applications and it will be explained how these beams are created in their respective production targets.