Cloud machine architectures face many drawbacks due to the improved autonomous and distributed IoT configuration. The IoT is closer to the cloud infrastructure. The fog offers IoT data care and storage locally on IoT devices rather than in the cloud. The fog provides quicker responses and better performance in relation to the cloud. The best alternative for IoT to provide powerful and effective resources for many IoT customers may therefore be called Fog Computing. This paper aims at fog computing's state-of-the-art and alignment with IoT in detailing the advantages and challenges of implementation. This study will concentrate also on the conception of cloud and fog technology and the application of the cloud and fog paradigm to improve modern IoT technologies. Finally, open issues and alternative research directions are discussed on fog estimation and IoT.