A default field that contains the host name or IP address of the network device that generated an event. Each event has a host field. The indexer generates the host field at index time. You use the host field in searches to narrow the search results to events that originate from a specific device.
You can configure host values for events when events are input into Splunk Enterprise. You can set a default host for a Splunk Enterprise server, file, or directory input. You can also have Splunk Enterprise assign host values to events based on data in those events.
For more information
In Knowledge Manager Manual:
In Getting Data In: