When a server has been configured to participate in replication either as a remote distribution server or as a combined publisher/distributor, it will have a database dedicated to replication distribution activities. The default name for this database is distribution, although the user setting up replication can change that name.
The distribution database is backed up in the same way as user databases, and it should be dumped regularly and frequently. The distribution database should have its transaction log on a separate device, so you usually can perform both database and transaction log dumps.
For more information about the distribution database see Part 6, Replication.