Every component on a computer requires software to interact with the operating system. Many devices will include a disc with the drivers on it so the user can easily install them without having to go to a site and download them first.
These discs will either be misplaced or lost when someone moves or the boxes that the devices are purchased in are thrown away. Many times the software that arrives on the discs are already outdated by the time they are used, and the manufacturers have newer versions available.
Many sites like DriversSoftware on the web are dedicated to having these drivers accessible all in one place. Whether you have updated your operating system and seeking the most compatible drivers or misplaced the software, this site has the drivers you might be looking for all over the web. They have hp drivers for that laser printer you depend on and ati drivers for that high-end video card you use to play the latest and greatest computer games.