As in Windows, every storage device, graphics, sound, or network adapter, pointing device, I/O port, and other peripheral device supported by Unix or Linux requires a device driver to convert the operating system's generic commands and data to the specific instructions and formats used by each device. Many of the most commonly used device drivers are included with most operating system software distributions, but others are new enough or obscure enough that you have to find and install them separately.
The first place to look for a Unix or Linux device driver is the Support section of the manufacturer's own Web site. Most hardware developers understand that Unix and Linux users can represent a small but important portion of their potential user base, so they develop and test versions of their own device drivers and control programs for Linux, and sometimes for other versions of Unix, along with the more popular Windows drivers.
If the manufacturer can't provide a driver for the version of Unix or Linux you're using, don't give up. One of the greatest strengths of these operating systems is the community of users and software developers who are anxious to help newcomers and to extend their favorite operating system to every imaginable type of hardware. So there's an excellent chance that somebody, someplace has created the driver you need, or possibly has produced a driver for a similar product that uses the identical controller chip set; if so, it can also work with your obscure device.
To find a device driver, try one of these methods:
Send a query to the manufacturer's Technical Support center, or ask a question in the User's Forum in the manufacturer's Web site.
Use Google or some other Web search tool to search for "[insert make and model here] Unix driver" or "[insert make and model here] Linux driver."
Look in the appropriate Usenet newsgroup for the version of Unix you are using. The archive of Usenet messages at http://www.groups.google.com contains messages dating back to the 1980s, so it's a valuable tool for searching through other people's requests and announcements. If you can't find what you need, post your own message, wait a day or two, and somebody will probably give you an answer. For Linux, try the comp.os.linux.hardware newsgroup. For Unix, look for a newsgroup in the comp.unix hierarchy. When you find the appropriate newsgroup, use the Search this group tool with "device driver" in quotation marks, followed by the make and model of the device you want to install.
Look for a link to sources of device drivers at the home page for your particular variety of Unix or Linux.