Herein paid attention to TMDs spin-valley coupling by providing a brief overview from before to current era information in the introduction. Additionally, based on theoretical concepts and experimental findings descriptions of the degree freedom and electronic structure, optical and electrical valley polarization, and valley coherence. To define the valleytronics properties of TMDs also discussed the valley-spin concept for monolayers (including selection rules for the valley and spin, valley Zeeman Effect and magnetic moment, valley Hall Effect and Berry phase effect, and nonlinear valley-spin currents through trigonal twisting) and Bi-layers in detail. Moreover, separate section discussions on inversion symmetry induced spin polarization and optics-induced Stark effect are also included.