This paper presents an overview of architecture and applications of the wireless sensor network. A Wireless Sensor Network is a type of wireless network. Basically, it consists of a collection of a number of tiny devices called the sensor node. These sensor nodes are set with radio interface with which they communicate with one another to form a network. A wireless sensor network (WSN) has important applications such as remote environmental monitoring and target tracking. This has been enabled by the availability, particularly in recent years that sensors are smaller, cheaper, and intelligent. These sensors are equipped with wireless interfaces with which they can communicate with one another to form a network. The design of a WSN depends significantly on the application, and it must consider factors such as the environment, the application’s design objectives, cost, hardware, and system constraints.