Wireless sensor networks are designed to remotely monitor physical or environmental attributes such as temperature, pressure, light, sound, etc. They generally comprise embedded system units consisting of sensing, processing, and communication units inside them. Such Wireless sensors can be deployed in extreme conditions like deep forests, high or low-temperature areas, industrial setup, etc. where continuous manual surveillance is not possible. In this paper, Wireless Sensor networks have been discussed in detail. Their architecture, operational characteristics, and challenges associated with setting up and managing the Wireless Sensor Networks have been discussed.