The problem if existing neutrinos are Dirac or Majorana particles is
considered in a very pedagogical way. After a few historical remarks we recall
the theoretical description of neutral spin 1/2 particles, emphasizing the
difference between chirality and helicity which is important in our discussion.
Next we describe the properties of neutrinos in the cases when their
interactions are given by the standard model and by its extensions (massive
neutrinos, right-handed currents, electromagnetic neutrino interaction,
interaction with scalar particles). Various processes where the different
nature of neutrinos could in principle be visible are reviewed. We clear up
misunderstandings which have appeared in last suggestions how to distinguish
both types of neutrinos.Comment: 38 pages, Latex, epsfig, 10 poscript files Presented at the XXI
Silesian School of Theoretical Physics on "Recent Progress in Theory and
Phenomenology of Fundamental Interactions", Ustron, September 199
