Ok, I'm guessing that you are trying out the free version of Splunk, and didn't actually buy a license. 🙂
Splunk is a tool for searching, correlating, reporting and alerting on (mainly) log data. Think of it as a powerful analytical tool, which also has capabilities to store data in its own internal format for a specified amount of time. Actually, you can decide to have different retention periods for different types of data.
It is not a backup tool, but it is commonly used for fulfilling internal/external requirements for centralized logging, i.e. to have important logs moved away from the systems where they were generated. So in a sense, the logs are 'backed up' to a secondary system, but usually logs would never be restored to the originating system in the event of a crash/attack/whatever.
I would guess that you could find the basic introductory videos on splunk.com, and a lot of detailed administrative tips on youtube.
/K
