Should tell you in the motherboard manual they are diagnostic indicators to tell you at what stage your Motherboard has got to which then gives you an idea whats wrong.
The manual isn't hugely helpful...
"2.7 Post Status Checker
Post Status Checker (PSC) diagnoses the computer when users power on the machine. It emits a red light to indicate whether the CPU, memory, VGA or storage is dysfunctional. The lights go off if the four mentioned above are functioning normally."
That's it; the sum total of help the manual gives. And as none of the lights stay lit, they don't really help much.

