A Port Expander is a hardware device designed to allow a user to utilize more than one device on a single port at one time. The two expander available are internal (has connection inside the CPU usually on the motherboard) and external that plugs into the existing port and then has multiple places to connect. http://www.wisegeek.com/what-is-a-port-expander.htmPorts: Place outside of PC where you can plug in a cable
USB portsnetwork ports, typically Ethernet and FireWirevideo ports, typically some combination of VGA, DVI, RCA/component, S-Video and HDMIaudio ports, typically some combination mini analog audio jacks or RCA legacy ports, or ports that follow old standards which are rarely used in modern computers, such as parallel printer ports and PS2 ports for a keyboard and mouse
Peripherals: Item added to a PC that is outside input and output devices: monitors, keyboards and mice. It also includes printers, speakers, headphones, microphones, webcams and USB flash drives
Expansion slot: Items that can be added to a mother board video cards, network cards, printer ports, TV receivers and many other custom additions but the card must match the expansion slot type. http://computer.howstuffworks.com/pc2.htmPort expanders are generic to items but can be used on just about anything on a computer.
Advantage
Able to connect more than one device to a single port.
Disadvantage:
The speed of the port is divided up among the devices connected to the port expander. I.E. A port expander connected to a 3 GBps port with 8 devices connected to the port expander will give a maximum of 375 MBps connection to each device