Install expansion cards

Expansion cards are cards such as:

• Sound cards
• Graphics cards
• Modems
• Network Interface Cards (NICs)
• etc.

They  normally go in PCI, PCI express, or AGP slots although there are other slots in older computers.  Expansion card slots are covered by metal tabs in the rear of your computer.

You can either add functionality to a computer by adding an expansion card or upgrade an existing card for better performance. 

Some reasons you may want to upgrade a card is for faster graphics for games or a more powerful sound card for better sound.  You may want to add a modem or NIC to access the internet or attach to a network.