The shortcomings of cloud computing model in high delay, high dependence on the network, excessive use of resources and low privacy protection are exposed when cater to the massive data transmission and real-time requirements in Internet of Things (IoT) application. Therefore the concept of edge computing has emerged, which refers to the enabling technologies allowing computation to be performed at the edge of the network. Edge computing can respond to user's needs more quickly and reliably because it is closer to the device and dose not rely on the WAN (Wide Area Network) connection. In addition, this local computing can improve personal privacy, as well as save network traffic and mitigate the computing pressure of cloud computing centers. Starting from the shortcomings of cloud computing, this paper illustrates the concept and general architecture of edge computing in the second chapter, and then elaborates two reference frameworks proposed by industry alliances. After that, we summarizes the four challenges of edge computing and their latest research progress in chapter four. The application of edge computing, which is a hot issue, are vigorously promoted by the advancement of scientific research in IoT field. For this reason, tow applications of edge computing in manufacturing and security monitoring are introduced at the end of this paper.