In recent years, Fog Computing is introduced as a powerful extension of cloud computing and services to the edge of the network. Similar to Cloud, Fog provides data, compute, storage, and application services to end users. The fog computing is used to reduce the workload of the cloud computing by bringing basic computing services and analytic services to the edge of network, providing computing resources closer to the end devices, mobility support, improving overall network efficiency and performance and low latency. We explore the different applications of fog computing and various key comparison between cloud computing and fog computing.