Hi-
That's the Startup Manager.
Any system icons?
Typically, an OS X icon (or more) will be present. Click on a system icon, and click the right arrow to boot to the selected system.
The circular arrow is "refresh" in case an expected system is not shown.
If there are no system choices, your current system may be damaged, or a drive may have problems.
Try booting to the OS X Install disc, open Disk Utility, and run "Repair Disk" on the startup drive.