It looks like you might have to give some info from that whole page of things you don't understand, 1st sentence, 1st paragraph, something like that...
As a guess I would say its the order of priorities your BIOS puts on which device to read from such as floppy, CD or hard disk. These priorities can be changed by going into the BIOS (usually done by a function key) and rearranging what disk to read from first. This is a once only setup so there is no need to carry out the procedure again.