A FireWire card is an add-in card that allows a FireWire device or peripheral to be connected to a computer. While some computers have built-in FireWire capability (including almost all Macintosh computers, but only a small percentage of Windows PCs), being able to add this functionality is of great benefit: FireWire is a faster method of data transfer than USB, Ethernet or wireless networks.
Apple Computer introduced FireWire in 1995. While the technology didn't catch on for a few years--many users were unaware of what exactly that "nuclear fallout symbol" meant--it wasn't long before tech-savvy users discovered the benefits of using FireWire for connecting hard drives.
In tech speak, IEEE 1394 interface is the formal term for FireWire. The original and still most popular type, the FireWire 400, featured the "classic" connector that is still widely used today. A second, faster version, FireWire 800, has gained traction, but has a different cable configuration, and is not as popular with casual users. FireWire cards are available with classic FireWire 400 ports, FireWire 800 ports or a combination of both; some cards even pair FireWire ports with USB or USB 2.0 ports.
While this technology is mostly associated with Apple computers, there are applications for using it on other platforms. An external FireWire hard drive can be shared between two computers (a Mac and a PC, for example) with no formatting necessary. Most video cameras have a FireWire output, which is used for transferring digital media directly to a computer. In addition, early models of Apple's iPod were strictly FireWire.
In addition to the faster data-transfer rate, the biggest advantage of FireWire is that devices can be daisy-chained ad infinitum. Apple's previous connectivity protocol, SCSI, had serious limitations in that area. Another Apple-specific feature is the ability to boot a Mac in "FireWire Target Mode." When you hold down the "T" key while booting, the computer functions as an external hard drive. This is an extremely fast, convenient way to copy large amounts of data from one computer to another.
FireWire cards are added to computers that either don't have one built in, or could use extra connections. Some of these cards are plug-and-play, but most generally come with software, and the drivers have to be installed. Despite manufacturers' claims to the contrary, these third-party cards, while fast, are rarely as "zippy: as comparable computers that feature a built-in FireWire port.