Spin angular momentum (SAM) and orbital angular momentum (OAM) are two absolutely different physical properties of light which are determined by the polarization and spatial distribution, respectively. The comparison of the two properties is performed in terms of demonstrated about the generation and conversion, existence form and description method, mechanical effect, spatial and time coherence, angular Doppler effect, parameter conversion and quantum entanglement, etc. The phenomenology provides much of the basis for the exploration and exploitation of the field. The progress of OAM development with an eye towards the promising future in the field is reviewed and analyzed.