I am just wondering if someone can explain to me the differences between the two modes stated above, I've looked online and can't find anything online that explains the difference, if there is any at all. I am using the RPi Model B.
It tells the library which pin nunbering system you are going to use. BOARD signifies using the physical pin numbers on the RPi P1 connector. BCM signifies the Broadcom SOC channel designation. One word of warning - the BCM channels moved around a little between revision 1 and revision 2 of the Raspberry Pi board. The BOARD numbering system stays working between board revisions.