That diagram shows a brief overview of essentially how Splunk works and what it does, so you'd have to be a bit more specific than that for a splunkbase question. If you want an overview of Splunk, the docs.splunk.com has all kinds of excellent information. The page http://docs.splunk.com/Documentation/Splunk/5.0.3/Installation/Splunksarchitectureandwhatgetsinstall... has this specific image and some info around it.
