A Replication Agent notifies Replication Server of actions in a primary database that must be copied to other databases.
The Replication Agent reads the database transaction log and transfers log records for replicated tables and stored procedures to the Replication Server managing the database, which distributes the modifications to databases that subscribe to the data.
A Replication Agent is needed for every database that contains primary data and for every database where stored procedures that need to be replicated are executed. A database that contains replicated data and no stored procedures marked for replication does not require a Replication Agent.
Replication Agents communicate with Replication Server by executing commands in Log Transfer Language (LTL).
See Replication Server Design Guide > Introduction to Replication Agents for more information about LTL commands.