USB cables have a USB connection on one end and a specialized connection on the other and are often designed to be used with a particular device. For instance, the USB cable designed to be used with a digital camera will not necessarily work with or have the correct connection to use it with an MP3 player. Manufacturers are making progress at deciding on a standard connection on the device, typically micro USB. One of the things that have made USB cables so prevalent is the fact that they have two power conductors which makes it possible to charge a device while it is plugged into a computer.
Other devices are starting to make use of USB connections as well as computers. HDTV's and even car stereos often have a USB port built into them so that a thumb drive or other device can be plugged in to play music or photos. It is possible the transfer data by means other than a USB cable, such as infrared and Bluetooth, but these methods are not as fast and they do not provide a means to charge the device in the process. Because of the incredible functionality of these cables, it is often handy to have a few extra lying around.
USB cables with a standard connection can be purchased at just about every major retailer. Even devices that require a specialized connector on one end will usually have a cable that matches them at most electronics stores. USB cables, for the most part, are pretty inexpensive but specialized models can cost a few extra dollars. The easiest and cheapest way to find exactly the USB cable that is necessary is to search for it online and purchase it from an online retailer. As with most types of cables, online retailers deliver significant cost savings over their traditional retail counterparts.