A USB hub is really nothing more than a gizmo with extra USB ports on it. You plug the hub into your laptop's USB port. Then you can plug anywhere from two to four to eight USB devices into the hub.
It may not seem practical, but your laptop can have up to 127 USB devices attached to it at any given time. Yes, all at once. That's one of the keys to the USB port's expandability.
Some devices cannot be run from hubs, such as certain high-speed hard drives. In that case, the device must be plugged directly into the computer's USB port. Don't fret: A warning message comes up and instructs you what to do when such a thing happens.
Keep your eye out for pass-through USB devices. This USB thingamabob sports an extra USB port somewhere on its body, so you can plug the USB device into your laptop and then plug another USB device into the first device. That way, you don't run out of USB ports.
There are two types of hubs: powered and unpowered. The powered hub must be plugged in or derive its power from the computer. Powered hubs are necessary in order to supply more power to some USB devices.
Obviously, a USB hub is probably not something you would want to pack in your laptop's case. The more cables the computer has, the less portable it becomes.
Note that smaller, more portable, laptop-size USB hubs are available. They’re very quaint — and more portable than the desktop, or full-size, USB hubs.
One of the best ways to add more USB ports to your laptop is to get them on a PC Card.