Universal Serial Bus or USB is a method that most computers use to talk to devices such as printers, scanners, wireless mice and keyboards. If you have more devices than USB spots on your computer, then you need to use a USB Host Controller to hook up your additional devices.
What is a Controller
Managing the data sent from your computer to each device is what a controller does. Most computers come with a common controller built in. These controllers help run your standard keyboard, monitor, mouse and even your printer. However if you are looking to add additional devices to your computer you will need an additional controller to manage those devices.
USB controllers need to be able to communicate with your computer's expansion bus. The bus is the collection of wires in your computer that connect all your device controllers and add-in cards in your PC. The three most common types of buses on a PC are the AT bus, the PCI bus and the SCSI bus.
Most of the time devices like printers, and scanners that are compatible with Windows XP are not compatible with Windows 7. The compatibility should be clearly marked on the box. This will save you the frustration of installing the product or even needing to return it back to your local store.