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Coaxial cable is an electrical cable consisting of a round, insulated conducting wire surrounded by a round, conducting sheath, usually surrounded by a final insulating layer. The cable is designed to carry a high-frequency or broadband signal, usually at radio frequencies. Coaxial Cabling is a two conductor closed transmission medium that is often used for the transmission of RF energy. It yields excellent performance at high frequencies and superior EMI control/shielding when compared to other types of copper cabling. Coaxial cabling is commonly found in broadcast and networking systems. Listed below are some common terms and definitions that are related to coaxial cabling:
 

STANDARD CABLE TYPES
Most coaxial cables have a characteristic impedance of either 50 or 75 ohms. The RF industry uses standard type-names for coaxial cables. The U.S military uses the RG-# or RG-#/U format (probably for "radio grade, universal", but other interpretations exist). For example:

Additional types of coaxial cable

The common RG-58 from Radio Shack is NOT the best you can do and will lower your effective power out! Use it only for short runs. So where does all this lost power go? Its dissipated as heat inside the cable. With a 100W transmitter you'll already notice your RG58 heating up after several minutes of operation which is definitely not what your want.

BELDEN makes terrific coax in various qualities and with low loss (measured in dB’s…decibels per 100m). 3dB loss = 1/4 of your signal strength - either lost or gained. Watch out for the correct impedance…RG-8 and RG-58 have 50 Ohms. RG-59 and RG-6 (Low Loss Version of RG-59) have 75 Ohms. Most antennas are 50 ohm and so are most transmitters.
Don't buy more than you need to make the long run to your antenna and don't make up a few "jumpers" to go between your exciter, VSWR meter and your antenna as all you'll do is create higher SWR and more line losses. Finally, don't use cheap TV cable!

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WHAT IS SWR (VSWR)

VSWR is a measure of how well two devices are impedance matched to each other. Typical radio equipment is designed for 50 ohm load impedance, so we usually use 50 ohm cables and build or buy antennas that are specified for 50 ohm. While most cables have a flat impedance over frequency (they measure 50 ohm at all frequencies you are likely to use), the same is not true of the antennas. A 1.0:1 VSWR is a perfect match. That means the load impedance is exactly 50 ohms. A 2.0:1 VSWR is obtained when the load impedance is either 25 ohms or 100 ohms. Because most transmitters will deliver full power with a load VSWR of up to 2.0:1, this value is usually considered the limit for acceptable operation. Many prefer to keep their VSWR below that however, but for all practical purposes, it is unnecessary to spend time or money trying to get much below a VSWR of 1.5:1. The benefits will be hard to measure and even harder to notice. On the other hand, coaxial cable losses increase rapidly, for a given frequency of operation, when the antenna VSWR exceeds 2.0:1. This can even, in some extreme cases, result in the coaxial cable burning, even when running 100 W. Using a higher grade of cable will definitely improve things, but even high quality coaxial cable becomes very lossy when VSWR exceeds 3.0:1 at higher HF frequencies (or VHF and higher).
 

COMMON CONNECTOR TYPES

"UHF" connector: The "UHF" connector is the old industry standby for frequencies above 50 MHz (during World War II, 100 MHz was considered UHF). The UHF connector is primarily an inexpensive all purpose screw on type that is not truly 50 Ohms. Therefore, it's primarily used below 300 MHz. Power handling of this connector is 500 Watts through 300 MHz. The frequency range is 0-300 MHz.

"N" connectors: "N" connectors were developed at Bell Labs soon after World War II so it is one of the oldest high performance coax connectors. It has good VSWR and low loss through 11 GHz. Power handling of this connector is 300 Watts through 1 GHz. The frequency range is 0-11 GHz.

"BNC" connctor: "BNC" connectors have a bayonet-lock interface which is suitable for uses where where numerous quick connect/disconnect insertions are required. BNC connector are for exampel used in various laboratory instruments and radio equipment. BNC connector has much lower cutoff frequency and higher loss than the N connector. BNC connectors are commonly available at 50 ohms and 75 ohms versions. Power handling of this connector is 80 Watts at 1 GHz. The frequency range is 0-4 GHz.

"TNC" connectors are an improved version of the BNC with a threaded interface. Power handling of this connector is 100 Watts at 1 GHz. The frequency range is 0-11 GHz.

"SMA" connector: "SMA" or miniature connectors became available in the mid 1960's. They are primarily designed for semi-rigid small diameter (0.141" OD and less) metal jacketed cable. Power handling of this connector is 100 Watts at 1 GHz. The frequency range is 0-18 GHz.

"7-16 DIN" connector: "7-16 DIN" connectors are recently developed in Europe. The part number represents the size in metric millimeters and DIN specifications. This quite expensive connector series was primarily designed for high power applications where many devices are co-located (like cellular poles). Power handling of this connector is 2500 Watts at 1 GHz. The frequency range is 0-7.5 GHz.

"F" connector: "F" connectors were primarily designed for very low cost high volume 75 Ohm applications much as TV and CATV. In this connector the center wire of the coax becomes the center conductor.

"IEC antenna connector": This is a very low-cost high volume 75 ohm connector used for TV and radio antenna connections around Europe.
Additional reading here.

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