Look on the back of your computer case, down at the bottom. The slot looking things are the expansion slots.
An expansion slot on the computer is basically add other hardware or peripherals, such as graphics cards, sound cards, and network cards. The expansion slots consist of usually 2 things. The first is...
PCI, PCI-E
it lets you add a sound,video card, wifi card ,things of that nature
An expansion slot is a device meant to hold