Twisted pair cable (most commonly Unshielded Twisted Pair in the US and Canada, and Shielded Copper Twisted Pair in the UK and Europe) is the primary means by which computer networks are strung together for data transmission. Shielded twisted pair cabling is more expensive, but has fewer issues with interference with other electronic devices.
Of these types of cables, there are two general categories - stranded (where each pair of copper communications conduits are made up of strands of wire braided together) and solid. Solid cable has better transmission properties, but is stiffer, and harder to bet into tight spaces, stranded is less expensive, easier to make into patch cables, but suffers performance degradation at medium distances (more than 10 meters). Within these categories are, well, categories. Category 3 cables are for general telephone usage, and most computer networks don't use it. (If you're experiencing strange connection issues, it's most likely due to Cat 3 cable getting involved somewhere in the line). Most of the cabling you use to hook up computers for networking, or, increasingly, electronics devices that need to communicate with each other, like the parts of a high-end home entertainment system, is Cat 5. Cat5 cabling is, in general, the former standard for most communications uses, and most legacy wiring is Cat 5. It's capable of 10 megabit and 100 megabit Ethernet connections, and is generally rated for a transmission capacity of 100 MHz (how quickly the electrical current cycles in the cable to send the signal). The current standard is an interim one, called Cat 5a or Cat 5e, which is an enhanced version of Cat 5 used for Gigabit (1000 Megabits per second) data transmission. It's got enhanced shielding, is usually made to finer tolerances, and has significant reductions in cross talk and between-line interference. If your network facility has been wired in the last three to four years, odds are its Cat 5a, as the cabling standard more or less replaced plain vanilla Cat 5 in the marketplace. The standard beyond Cat 5a is still being debated by the governing bodies; many manufacturers are jumping the gun on the formal standard, and are releasing Cat 6 cable. Like the prior cable types, it's made up of four pairs of twisted copper wire; what makes it different is a longitudinal separator between the wires; which isolates each of the four pairs from one another. This significantly reduces cross talk, and modestly increases the manufacturing cost (and the prices of the cable and firmware). If your networking application is looking to go to 10 Gigabit Ethernet, Cat 6 is the way to go. It will operate at up to 250 MHz, which greatly improves transmission speeds; it's also got a 500-metre transmission distance, and is generally better all around. If you can afford the 10% premium or so for Cat 6, the general advice is to run it. Even if you're current hardware can't put out the speeds the cable is rated for, replacing a router is a lot less painful than redoing all the cable runs in a data centre or an office building. [Non-text portions of this message have been removed]
