IoT is an emerging technology which allows intelligent interaction between people and things. It focuses to combine everything in the world under a single infrastructure. So, it means the connection of devices using embedded software, sensors and actuators to communicate with one another. IoT aims to unify everything in our world under a common infrastructure, giving us not only control of things around us but also keep us informed on the state of things. In this Paper, we review a concept of IoT applications and security challenges that facing the implementation of the IoT. IoT is quickly developing across industries all over the globe. There are many success stories that demonstrate the value in every organization but the market has not been able to recognize the benefits of IoT. IoT is expected to be a rapidly developing technology. IoT can improve communications in an organization, bringing innovation in businesses, increase customer engagement and help in assessing the work process. IoT is used to automate data collection, processing, and analysis from various sources.