It is used to duplicate a git repository from gerrit to anyway. Configuration file is $GERRIT_INSTALL/etc/replication.config.
Config file example to clone MyRepo from gerrit to backupServer
[remote "backup"]
url = ProjectUrlOnBackupServer/${name} #Example backup.some.org:/pub/git/${...
This plugin is mandatory to make Gerrit able to receive message from other services. As an example, it has to be install to use Sonar Gerrit plugin
Install jar file under plugins folder
Default configuration is sufficient