Advances in hardware and wireless network technologies have created low-cost, low-power, multifunctional miniature sensor devices. Sensor networks are dense wireless networks of small sensors, which collect and disseminate environmental data. The collected data or information is processed, interpreted and accordingly actions are performed. Wireless sensor networks facilitate monitoring and controlling of physical environments from remote locations with better accuracy. Even they have applications in a variety of fields such as environmental monitoring, military purposes and gathering sensing information from hostile locations. Sensor nodes have various energy and computational constraints because of their inexpensive nature and ad hoc method of deployment. Some challenging areas in the sensor networks are reduced energy consumption methods and effective routing techniques.