Distributed Computing System is a collection of systems that are distributed at different remote sites and are connected via a common network such as LAN, WAN, etc. and are capable of collaborating a task. Distributed Computing involves computing performed among multiple network-connected computers.
When a task is given it is shared among all the computers connected in a network. The user on one computer may access the resources from some other remote computers connected in the network.
WWW is a good example for distributed computing where one request for a file or web page from the browser, the file may be fetched from yet another remote server or computer.