Client/ Server Architecture:  

As the capacity and power of personal computers improved, the need to share the processing demands between the host server and the client workstation increased. This need for greater computing control and more computing value led to the evolution of client/server technology.  In client/server architecture, the tasks or workloads are partitioned as:  

• server programs - providers of a resource or service  
• client programs - requester of resource or service

Clients and servers may reside in the same machine or they typically reside in separate pieces of hardware and communicate over a computer network. A server machine is  a host that runs one or more server programs which share their resource with clients. A client does not share any of its resources, but requests a server function or service. The server program fulfills the client request. Clients initiate a communication session with the server. The client/ server system may be two-tiered, three-tiered or n-tiered.