The short answer is Cat5e.
Cat6 rated cable is the latest common standard but it costs almost twice as much and in offers the same network speeds as Cat5e. If you're asking what kind of ethernet cable you should buy then the few cases where Cat6 makes a difference are on the very edge of the bell curve and almost definately not needed.
What Do You Need From Your Network Cable?
Practically any computer today has a gigabit network card which is 1000 Mb/s. The good news is that Cat5e cable supports this – no problem. You will also need a network switch that is gigabit or 1000Mb/s. Almost all switches today are Gigabit. Cat5e cable easily operates at the maximum capacity of your office network.
Are Gigabit Speeds Required?
Basic human nature is to get the most and go the fastest and gigabit is the fastest your computer will support however consider your internet speed. Most computers in home or at the office are connected with a network cable exclusively to access the internet. For most people Internet plans are 6Mb, 15Mb, 25Mb and a really fast plan plan might be 50Mb. These speeds are significantly slower than 1000Mb. I would argue that the older 100Mb/s networking standard will give no difference in speed to your computer.
If you have a server that you share files on then you're in a position to use the extra capacity of a gigabit network. Opening large files like video, pictures, drafting or even Quickbooks, can be a good reason to go with Gigabit. Cat5e network cable remains capable at delivering the full gigabit speeds.
Why would I want to install Cat6 cable?
When having your network cable professionally installed, the cost of the cable is a fraction of the cost of installing the cable. Even though Cat6 cable is twice as much and the cable ends are twice as much as Cat5e cable, for a small percentage on the total cabling cost, you have "better" cable.
10 Gigabit Networks
There is a faster 10 Gigabit standard thats been out for a number of years. 10 Gigabit network will run on Cat6 cable but they will not run on Cat5e network cable. Frankly, the 10 Gigabit standard has been out for over 10 years now and its still extremely rare to find it in small and medium sized businesses. To run 10G internet to your computer you would also need to install extra expensive network cards in your computer and buy expensive network switches that support 10g. The network switch alone will be 10x + more expensive then the network switch you're currently using. 10g networks for small and medium networks has simply not caught on because it doesn't provide a significant improvement over gigabit networks and is not economically fiesable with all the additional costs. Cat 6 cables are limited to 150ft for 10 gigabit networks where the standard max for 1 gigabit networks is 330ft.
Cat6A Network Cable
If you seriously think you need 10G internet in the next 5 years, we recommend using Cat6A network cable. Cat6A network cable is a step up from Cat6 and can properly run 10G ethernet even over longer 330ft cable lengths.
What Else Do I Need to Know About Network Cable?
Riser, Plenum and LSZH
The jacket (covering tha surrounds the 8 wires) is made out of PVC plastic. When there is a fire and the network cable burns, the PVC plastic gives off toxic smoke and lots of it. Some building code requires the use of cable that uses a different jacket that is less toxic when burned and gives off less smoke, this is Plenum rated cable. There is also a LSZH rated cable that is "Low Smoke – Zero Halogen" that has even better characteristics when burned. Typically the higher Plenum rated or LSZH cables should be used in commercial spaces where there is a air return that is part of the buildings environmental system to minimize the transmision of smoke and toxic air during a fire.
Riser cable is the least expensive but has a strain-relief "strength member" thread that helps the cable resist stretching when hanging from vertical floor-to-floor installations.
For most installations the cheaper Riser cable is adequate unless plenum is specified by the building code.
Network Cable Comes in Different Colors
Standard network cable is blue. If you are running it on the surface of a wall or ceiling you may want to use black or white to help it blend in more. Other colors are available to help color code your cables.
Outdoor Ethernet Cable
Special network cable is available that is designed to be burried in the ground. The outside jacket on these cables is designed to better handle moisture and not break down in broader weather and while burried.
Outdoor Network Cables for Antennas
If you are using the cable to connect to an outdoor wireless antenna, you should get network cable that has an ESD drain. The air outside becomes charged with energy when there are weather storms. Antennas are good at picking up this energy and do a good job of using their copper wires to transmit that energy down to the networking equipment. The networking equipment does not like this and it will often destroy the equipment.
Network cable can be ordered with an extra ESD drain conductor. This conductor is designed to carry the extra energy so that the standard network conductors won't. The ESD Drain is then connected on both side of the cable using special network jacks which will release the energy to the earth via the standard ground conductor of any 120v electrial plug.
Shielded Cable.
Cable can also be shielded. the Shield is a thin metal wrapper that is under the plastic jacket and wraps the ethernet conductors in network cable. This protects the signal on the cable from magnetic flux that will degrade the electric signal on the cable. Equipment like florecent lights, motors, compressors and others, give off RF interference and magnetic flux which degrades the electrical signal on network cables. A shield in the network cable can help reduce this. When installing shielded cable, the equipment on both sides of the cable must be designed to accept shielded cable. Any patch panel connectors also must be shielded connectors and the equipment should have a dedicated ground for the shield to give any value.
More Advice
Always run extra cable drops. As the story goes, if you run an extra cable, you'll never need it however, if you don't, there will be need for an extra very shortly.
Summary
There are different types of ethernet network cable available. The most common is Cat5e which performs at maximum capacity for small and medium business and is half the price of the more recent Cat6 standard. We recommend Cat5e cable for most installations.