From wikipedia
"
Flexible flat cable, or
FFC, refers to any variety of electrical cable that is both flat and flexible. However, the term FFC usually refers to the extremely flat cable often found in high density electronic applications like laptops and cell phones. FFC is a miniaturized form of
ribbon cable, which is also flat and flexible. The cable usually consists of a flat and flexible plastic film base, with multiple metallic conductors bonded to one surface. At each end the cable is slightly thicker to aid insertion and removal."
and flex can be used in a variety of ways for different purpose... in the diamond, im not sure what it does... but theres some in the pro, which connect the keyboard to the screen, to display the text input
Hope this helps