Replication is the process by which data and database objects are distributed from SQL Server to other database engines that reside across an enterprise; this data can be distributed to other SQL Server databases or even nonSQL Server databases such as Oracle and others. Replication can be explained by using a publisher/subscriber/distributor metaphor. To understand replication, you must understand and become familiar with the basic concept of the publisher/distributor/subscriber metaphor. This metaphor defines the different roles SQL Server can play in the replication process. Each role provides functionality that aids in the replication process:
Publisher In replication terminology, the publisher is the server that produces the original data for the use of the replication process. The publisher can produce many publications or sets of data to be distributed to other subscribing machines. One publisher can produce data to be replicated to many subscribers. Also, many publishers can produce data to be distributed to just a single, central subscriber. The former is implemented as a standard central publisher/distributor/subscriber replication model, and the latter is referred to as central subscriber replication.
Distributor The distributor is the server that contains the distribution database, data history, and transactions; as its name implies, it sends data to subscribers. The distributor can be implemented on the same physical server as the publisher or subscriber, although it doesn't need to be. It can reside on a separate server somewhere else in the world and be connected via a network. The placement of the distributor and its characteristics depend on the type of replication used.
Subscriber A subscriber, in SQL Server terms, is the server that receives replicated data through the distributor. Subscribers can choose from the publications available at the publisher and don't necessarily need to subscribe to them all.