ANSI (American National Standards Institute) Standard #568 describes the different types of categories (or Cat when talking about a piece of cable). The three most popular and widely used cables are Cat 5, Cat 5e, and Cat 6. It is important to pick the right category cable for the project that you are doing. The reason why it is important is because you will know that you will be able to obtain a certain level of performance from your network by having installed the correct category cable.

Cat 5
Category 5 cable can be used to carry Ethernet traffic of up to 100Mbit/s and ATM of up to 155Mbit/s. The standard cable of an Ethernet 100Base-TX is Cat 5. Cat 5 is a twisted pair cable created for high signal integrity. Some are unshielded while others are shielded. Cat 5 is used in structured cabling for computer networks, token ring, basic voice services, and ATM. The Category 5 cable has four twisted pairs in a single cable jacket. Cat 5 generally has three twists per inch of each individual twisted pair of 24 gauge wires inside of the cable.

Cat 5e
Category 5e is an upgraded version of the Cat 5 standard and is capable of carrying data up to 1000Mbit/s. Cat 5e is the standard cable for use in Ethernet 1000Base-T. Cat 5e is able to carry data longer distances than Cat 5. Cat 5e can be used confidently for 350 meters. Cat 5e has better performance measures. It also has more complex internals. Cat 5e exists in both solid conductor forms and stranded forms. Stranded is much more flexible and is used for military applications. Cat 5e is terminated in two different schemes, but there is no difference in the scheme used.

Cat 6 is similar to Cat 5e but is designed with even stricter standards. Cat 6 is backward compatible with Cat 5/Cat 5e. Cat 6 has a standard performance of 250 MHz and works with both 1000BASE-T and 10BASE-T / 100BASE-TX. It also works with 10GBASE-T standard, but there are limits if Cat 6 unshielded cable is used. Like earlier Cat 5e/ Cat 5, Cat 6 contains four twisted copper wire pairs. The cable is made usually with 22 to 24 AWG gauge wire. Cat 6, when used in a patch cable function, is often terminated with a RJ-45 connection.

One may use Cat 5, Cat 5e, or Cat 6 in the same project, but the signal will be limited to the lowest category copper cable. When deciding on which category cable to use, make sure to pick a cable that not only meets your current needs but your future needs as well.