Grid computing is a phrase in distributed computing which can have several meanings:

* A local computer cluster which is like a "grid" because it is composed of multiple nodes.

* Offering online computation or storage as a metered commercial service, known as utility computing, computing on demand, or cloud computing.

* The creation of a "virtual supercomputer" by using spare computing resources within an organization.

* The creation of a "virtual supercomputer" by using a network of geographically dispersed computers. Volunteer computing, which generally focuses on scientific, mathematical, and academic problems, is the most common application of this technology.

These varying definitions cover the spectrum of "distributed computing", and sometimes the two terms are used as synonyms. This article focuses on distributed computing technologies which are not in the traditional dedicated clusters; otherwise, see computer cluster.

Functionally, one can also speak of several types of grids:

* Computational grids (including CPU Scavenging grids) which focuses primarily on computationally-intensive operations.

* Data grids or the controlled sharing and management of large amounts of distributed data.

* Equipment grids which have a primary piece of equipment e.g. a telescope, and where the surrounding Grid is used to control the equipment remotely and to analyze the data produced.