When you buy a new computer these days, connectivity is an important consideration. In short, computers by themselves aren't the whole story, it's the things that we can add on to them that make them fun: printers, cameras, scanners, mobile phones and so on.
In the old days it used to be a matter of buying an adapter card to stick in the back of your machine for every new device you wanted to add.
Nowadays, it's a lot simpler, but there are two different connection standards you need to understand: USB (Universal Serial Bus) is a plug-and-play interface between a computer and add-on devices. With USB a new device can be added without having to add an adapter card or even having to turn the computer off.
FireWire, Apple's trademark name for the IEEE1394 standard, is a fast and versatile interface used to connect digital video cameras, and other applications that move large amounts of data, to computers. To get really techy: FireWire is inherently peer-to-peer, which means it can sustain its transfer rates without taxing your computer's internal resources. USB, however, needs more of your computer's resources to maximise its transfer rates. So, theoretically, FireWire can sustain its maximum transfer speed for longer.
It used to be a simple choice: Mac users had FireWire, which could handle the fun stuff like DVD burners, video cameras, external hard drives, and so on, whereas PC users were confined to using the slower USB connection, which could only handle mice, printers and scanners. However, all that changed with the introduction of USB 2.0, which pumps up the USB performance to make it a viable competitor to FireWire. USB 2.0 operates at a speed of 480Mbps* and FireWire at 400Mbps.* Although FireWire does not come as standard on many PCs, it is available as an add-on card. So deciding which standard to use depends largely on the peripheral. In many cases this will make the decision for you, since most external devices only have one type of port.
However, for your own reference, in general, tests show that FireWire delivers better performance for external hard drives, for CDDVD burners there's not a lot in it, and for printing and scanning USB is perfectly adequate. If you're doing any sort of digital video work then FireWire still continues to be pretty much a prerequisite.
Now go and get connected!
* Mbps (mega bits per second) is a measure of the total information flow between two devices. To give some idea of comparison, the fastest internet connection you're likely to have at home will run at about 5 Mbps.