"Mother bored".
Its motherboard or mobo for short.
Well, as long as your card have a PCIe slot you can use a GTX 980 on it.
About the case it'll most likely fit. All the cards tend to have the same size so you should be just fine.
Just one thing: if your CPU is really old and outdated you may experience some bottleneck.
Also don't forget to check if your PSU can deliver enough power to the system with the new card.