Boot menu on dell computers

Hi,

On computers now especially on Dell machines, when the power button is pressed,
and when the computer is going through the initialization POST screen, there is
an option to press F12 to get to a boot up screen where selections can be made
to boot up from either the hard drive or a cd-rom.

Also, when I use diskpart command i the System Recovery Console or when I go to
install Windows XP, there are two partitions listed. The first is the partition
which iI think is a FAT partition thats like 31 MB. The second is the main one
which takes up the rest of the hard drive.

My question is, which is the active partition, which is the system partition,
and which is the boot partition??

Also, how does this setup work as compared to when a computer would have only 1
partition for everything which was the active partition, and no F12 boot menu
screen??

Thanks.