Our introductory notes presented by V.G.Farafonov give the definitions of such basic optical characteristics of non-spherical scatterers as amplitude and scattering matrices, different cross-sections, asymmetry factor, etc. Special attention is paid to the differences between these definitions and those for spherical scatterers. ... 2000). The PostScript version of the notes is here . ... Created by V.I. Last modified: 10/05/03, V.I. ...