Network speed ,storage capacity and processor speed is increasing every year, but at the same time a large portion of the computing capacity is left unused .So we go for grid computing. Grid computing is an emerging technology, where we can unite a pool of servers, PCs, storage systems and networks into one large system to deliver nontrivial qualities of service.For an end user or application it looks like one big virtual computing system.Grid computing is a network of computation. Grid technology allows organizations to use numerous computers to solve problems by sharing computing resources.These resources could be hetrogeneous or distributed across the globe. So we need open standards and protocols. The architecture for grid computing is defind in Open Grid Service Architecture (OGSA) developed through the Global Grid Forum. OGSA defines what grid services are and the overall structure and services to be provided in grid environments.The key components in grid computing are portal or user interface, security, information service, scheduler, data management, job and resource management. Industries using grid computing now are automotive and aerospace, financial services, life sciences, government organisations like military departments, advanced data and compute intensive research.