  This is a summary of a series of lectures on the current experimental and
theoretical status of our understanding of origin and nature of cosmic
radiation. Specific focus is put on ultra-high energy cosmic radiation above
~10^17 eV, including secondary neutral particles and in particular neutrinos.
The most important open questions are related to the mass composition and sky
distributions of these particles as well as on the location and nature of their
sources. High energy neutrinos at GeV energies and above from extra-terrestrial
sources have not yet been detected and experimental upper limits start to put
strong contraints on the sources and the acceleration mechanism of very high
energy cosmic rays.
