Distributed, in an information technology (IT) context, means that something is shared among multiple systems which may also be in different locations.
In distributed computing, processing and data are spread out over multiple computers, usually over a network. Years ago -- prior to low-cost computer power on the desktop -- computing was organized in centralized "glass houses" (so-called because the computers were often shown to visitors through picture windows). Today, most enterprises locate applications and data where they can operate most efficiently, to some mix of desktop workstations, local area network servers, regional servers, Web servers, and other servers.
The cloud model, in which data and applications are served to users over the Internet, is a particular implementation of distributed computing, as is grid computing, in which large numbers of often geographically dispersed systems work together to perform compute-intensive tasks.
The Distributed Computing Environment (DCE), a standard developed in the early 1990s, was influential for subsequent distribution models. Current models for distributed computing include client-server, clustered, n-tier and peer-to-peer (P2P).
A few examples of distributed systems:
In a distributed database, portions of the database are stored on multiple computers within a network. Users have access to the portion of the database at their location so that they can access the data relevant to their tasks without interfering with the work of others.
A distributed antenna system (DAS) is a network of relatively small antennas installed throughout a building to serve as repeaters. A DAS is designed to overcome the problem of isolated spots of poor coverage inside a large building.
Distributed learning systems involve remote instructional delivery that may include Web-based content, streaming video, videoconferencing and other combinations of electronic and traditional educational models.
A distributed file system (DFS) is a client/server-based application that allows clients to access and process data stored on the server as if it were on their own computer.
A distributed denial-of-service (DDoS) attack is a DoS attack in which a multitude of compromised systems attack a single target, thereby causing denial of service for users of the targeted system.