Grid computing involves connecting geographically distributed computers and resources into a single network to create a virtual supercomputer. Key aspects of grid computing include combining computational power from multiple computers, providing single sign-on access to distributed resources, and distributing programs across processes or computers. Popular software for implementing grids includes Globus, Condor, Legion, and NetSolve. Grids are useful for tasks like distributed supercomputing, high-throughput computing, and data-intensive computing.