Commonly referred to as an ethernet, LAN, and/or patch cable, there are several variations of twisted-pair copper cable used to transmit data in network applications. The prefix “Cat” is shorthand for Category and the subsequent number designates the grade and capabilities of the cable. Together, the combination of the two place the cable into various categories based on satisfaction of specific product standards set forth by the Telecommunication Industry Association (TIA) and Electronic Industries Association (EIA). The general difference between Category 5 and Category 6 cable lies in their speed, capacity, and capability of data transmission.
Cat 5: Category 5 cable is the more basic of the two cables in question, available in two varieties. They are Unshielded twisted pair (UTP), most commonly used in the United States, and Screened Twisted Pair (SCTP), which has a shielding to provide extra protection against interference [rarely used outside of Europe]. Cables belonging to Category 5 are either solid or stranded. If data needs to be transmitted over a long distance, solid Cat 5 is a more proper choice as it's more rigid. Stranded Cat 5 is very flexible and most likely to be used as a patch cable (a cable used to connect to a nearby network hub, switch, router, etc). Cat 5 cable can support 10 or 100 Mbps Ethernet, with a capability of up to 100 MHZ.
[There is also Cat5e cable, which essentially Cat5.5 – not quite as advanced as Cat 6, but with more data transmission power than Cat 5. The 'e' of this cable stands for enhanced, and it's become a pretty widespread replacement for Cat 5 in newer installations. Cat 5e handles data transfer at 10x more of a capacity than Cat 5 at 1000 Mbps, and is well-suited for Gigabit Ethernet]
Cat 6: Category 6 cable is the standard for any Gigabit Ethernet connection and is backwards compatible with Cat 5/5e cables. Similar in structure to Cat 5 cable, Category 6 cable is made up of four twisted pairs of copper wire. The main difference is a longitudinal seperator, which isolates the pairs from one another, reducing crosstalk (undesired interference) and allowing for faster data transfer. In fact, Category 6 cable has twice the bandwidth of Cat 5, ideal for supporting 10 Gigabit Ethernet, operating up to 250 MHz. Cat 6 cable is a favorable option in case future updates demand a greater amount of data transmission.
[The latest standard for twisted pair cable systems is Cat 6a (or Augmented Category), defined at frequencies up to 500 MHz — twice that of Cat 6]
Current applications running at 1Gb/s are really pushing the limits of Category 5e cabling. In addition to this, streaming of of media applications such as video and multimedia increase bandwidth strain, necessitating faster data rates and applications that benefit and sometimes demand the higher performance of Category 6 cable. Bandwidth precedes data rates in the same way highways are built to accommodate an expected flow of traffic…doubling bandwidth is in essence, the same as doubling lanes on a highway. On average, data rates have been doubling every 18 months, which in turn has mandated an evolution in cable standards. Category 5 cable still remains the industry standard while Cat 6 and and Cat 7 are currently in development.