Over recent years there is a huge growth in the area of wireless networks due to its efficient design. The word sensor is defined as component which handles & monitor different kinds of inputs from different sources such as physical and environmental conditions like pressure, heat, light, sound and vibrations etc. The output produced by the sensor will be electrical in nature and this electrical signal is further applied to various controllers for other functions. A Wireless Sensor Network is basically a form of ad-hoc network which consists of thousands of tiny sensor nodes. These wireless networks are deployed where the wired network implementation is difficult or impossible. These nodes are further distributed over a wide area such as hilly areas, forests, deserts, ocean etc. and these tiny sensors communicate or exchange data with each other by using radio signals. The WSN utilizes various communication protocols like Bluetooth, Wi-Fi, Zigbee and Ultra Wide Band techniques. Every protocol has its own speed and depending upon the distance between them, there are various problems which network can face like battery failure, effective coverage area, and effective energy utilization or node failure. In this paper, the several different methods to build energy efficient network, methods to improve the lifetime of a network, method for detection and correction of node failure and in the last the important applications are discussed.