Superfluid 3He: introduction to the subject

In the review an account is given of the basic experimental results and of the theoretical concepts concerning the superfluid A and B phases of 3He. A and B phases of 3He possess the most complicated order parameters of all the ordered known media so far. It results in a rich spectrum of the properties of these phases: magnetic, acoustic, superfluid and others. The theoretical description of the structure of phases has been carried out on the phenomenological level which employed only general concepts on the Cooper pairing with a nonzero angular momentum and a totality of experimental data. A separate chapter is devoted to the linear and nonlinear NMR in superfluid 3He. The experiments and theory of NMR are very mUch important in understanding the structure of superfluid phases of 3He