Riser
yes, its what enables the video card to be attached to the motherboard if I understand your question right
True
Yes, NICs can be a form of expansion card (as long as the NIC is not built into the motherboard).
it is used to connect expansion cards to the Motherboard
True
Yes they are... The motherboard is a large, square circuit board, containing lots of sockets. Expansion cards are rectangular circuit boards that slot into the sockets on the motherboard.
PCI
slots.
ports
fef
That is difficult to say without knowing the cards intended use. Some cards plug into expansion slots on motherboards. Some plug into risers. Some expansion cards are actually daughter cards that plug into another card.
No, they are very different. The motherboard is the board (usually green) to which all of the other components are attached. The harddrive (usually listed as C:, or local disk C, where all of the data is stored.