Database replication is the process by which data is kept uniform throughout a system. In some instances, database replication means simply copying data from one source to another. When a more robust replication process is required for complex networks, regular updates can be logged to data, ensuring that all new changes are reflected throughout the system. This process is called transactional replication.
Further reading: http://en.wikipedia.org/wiki/Data_replication#Database_replication http://searchsqlserver.techtarget.com/definition/database-replication