Abstract: Neural-network quantum states are states represented by artificial neural networks. Thanks to the dramatic progress achieved recently in the field of machine learning, especially deep learning, the study of neural-network quantum states has attracted tremendous attention across communities, and has become one of the most active directions of research. In this paper, we review different kinds of neural-network quantum states, their physical properties, and typical applications. In addition, we also discuss some most recent advances and future challenges along this direction.