Quasi-symmetry concepts in helical systems are briefly explained. The one of the magnetic coordinates, Boozer coordinates, are the essential basis for considering quasi-symmetry concepts in terms of drift trajectories and neoclassical transport properties. Several features of quasi-symmetric (quasiaxisymmetric, helically symmetric and poloidally symmetric) concept are briefly described from the viewpoints of configurational properties. The intuitive classification of these concepts (including (quasi-)isodynamic concept) is also given.