When the network is as fast as the computer's internal links, the machine disintegrates across the net into a set of special purpose appliances.
-- Gilder Technology Report, June 2000.
“United we stand, divided we fall”, is the key idea behind grid computing. Grid is a type of parallel and distributed system that enables the sharing, selection, and aggregation of geographically distributed "autonomous" resources dynamically at runtime depending on their availability, capability, performance, cost, and users' quality-of-service requirements.
Grid computing is a critical shift in thinking about how to maximize the value of computing resources. It allows us to unite pools of servers, storage systems and networks into a single large system so we can deliver the power of multiple-systems resources to a single user point for a specific purpose. To a user, data file, or an application, the system appears to be a single, enormous virtual computing system.
Grid computing is the next logical step in distributed networking. Just as the Internet allows users to share ideas and files as the seeds of projects, grid computing lets us share the resources of disparate computer systems. The major purpose of a grid, is to virtualize resources to solve problems. So, rather than using a network of computers simply to communicate and transfer data, grid computing taps the unused processor cycles or numerous i.e. thousands of computers.