In this paper author aims at describing a wireless sensor network. wireless sensor network consisting of spatially distributed autonomous devices using sensor to monitor physical or environmental conditions. Wireless sensor network can be used in wide range of applications including environmental monitoring, habitat monitoring, various military applications, smart home technologiesand agriculture. Wireless sensor networks constitute one of promising application areas of the recently developed wireless sensor networking techniques. Various clustering Schemes have been discussed and employed in both homogenous and heterogeneous wireless sensor network.