With the increasing scale of the Internet, network management and operations become extremely complex. Intent-based networking (IBN) emerges when network autonomy becomes a major trend of future network. First of all, this paper gives the definition of IBN, and describes the IBN category and architecture in academia and industry. The implementation closed-loop of IBN is also summarized, including intent acquisition, intent translation, policy verification, intent distribution and execution, real-time feedback and optimization. Then, key technologies of IBN implementation are elaborated in detail according to the IBN closed-loop. In addition, examples are given to illustrate the IBN-based applications from the aspects of network measurement and network service orchestration. Finally, the future research work is prospected and the whole paper is concluded.