Graylog Sidecar controls the agents in your environment while maintaining a consistent configuration across the hosts via a tag system. Tags are created via the Web Console, containing the configuration for the collection type (e.g., Apache logs, DNS logs).
Once the system has the tag applied to the endpoint, it automatically starts collecting the logs and bringing them into Graylog. Snippets can also be used, to provide additional configuration of the agent when it may not be possible via system.