1. Introduction
2. Datasets
2.1. The KTH Dataset
2.2. The Weizmann Dataset
2.3. The IXMAS Dataset
2.4. CMU MoBo Dataset
2.5. HOHA-1 (Hollywood Human Actions I) Dataset
2.6. HOHA-2 (Hollywood Human Actions II) Dataset
2.7. Human Eva Dataset
2.8. CMU Mocap Dataset
3. Single-layered Approaches
3.1. Advances in Space-Time Approaches
3.2. Sequential Approaches
4. Hierarchical Approaches
4.2. Syntactic Approaches
4.3. Description-based Approaches
5. Conclusion