Replication means copying the data on one database server to another server, as well as syncing the copies so they behave nearly identically.
According to the Microsoft TechNet SQL Server Glossary, replication is “the process of copying updated data from a data store or file system on a source computer to a matching data store or file system on one or more destination computers to synchronize the data.”
Replication is the process of copying data or changes in data from one database to another. The goal of replication is to create a nearly identical database. Any number of databases can be replicated (ie, updated to be in sync), so the changes made in one version of the database will be updated in all versions.
The key benefit of replication is the creation of a distributed database system. A distributed system makes it possible for many users to work with their own local copy of a database, but all the versions are updated as if it were a centralized database.
Replication is extremely useful for larger enterprises with database applications where users are widely geographically distributed. Furthermore, with replication, even if one database instance becomes unavailable, users can continue to query and update the remaining locations.
Partial Replication — Unlike full replication which transfers copies of all data items to all versions, partial replication only copies a limited set of data item to some or all versions. Full replication is often too resource intensive when an application has a high update workload. Partial replication is less resource intensive as each version only has to execute the updates for data items for which it has local copies.