This book provides a unified combinatorial realization of the categroies
of (closed, oriented) 3-manifolds, combed 3-manifolds, framed
3-manifolds and spin 3-manifolds. In all four cases the objects of the
realization are finite enhanced graphs, and only finitely many local
moves have to be taken into account. These realizations are based on the
notion of branched standard spine, introduced in the book as a
combination of the notion of branched surface with that of standard
spine. The book is intended for readers interested in low-dimensional
topology, and some familiarity with the basics is assumed. A list of
questions, some of which concerning relations with the theory of quantum
invariants, is enclosed.