Composite Video terminals are the old standard "A/V" jacks you're probably familiar with. A composite video cable delivers both chrominance (color) and luminance (light/dark or grayscale) information along the same cable. While composite video is far inferior to Component Video, it's still capable of producing a good picture, and may be your only option for VCRs and some cable boxes. Be sure to use a high-quality composite video cable for best results.
S-Video uses a 4-pin rounded plug to separate the chrominance and luminance signal, which theoretically should improve picture quality over the standard composite video "A/V" connection. In practice however, we've found that most of today's plasma televisions perform just as well, or even better, with the composite connection: the video processing circuits in the plasma will do a fine job of separating the information once it reaches the monitor.
The best of the analog video connections, component video terminals are found on almost any plasma TV you'll be considering, and can be used for progressive-scan DVD, HDTV, and your higher-end cable and satellite boxes. One important note is about the bandwidth of the component video terminal: if you want to use your component inputs for HDTV, look for component inputs called "high-bandwidth" or "HDTV component video" to ensure the terminal can handle the extra information passed through an HDTV signal.
DVI (Digital Visual Interface)
DVI is a multi-pin plug used to transfer video information in an all-digital format. Because the signal undergoes less digital-to-analog conversion, DVI should result in a sharper picture with less conversion artifacts. Most DVI outputs provided by Home Theater gear will be of the DVI-D type, which only carries digital signals, and usually supports the HDCP (High Bandwidth Digital Content Protection) standard of copy protection used by many HDTV providers.
Many PC video cards use DVI outputs as well, and you may find plasmas with DVI-I terminals, which support both digital and analog signals. If you see a DVI-I terminal on a plasma which does not support HDCP, it's most likely intended for PC use.
HDMI (High-Definition Multimedia Interface)
To take advantage of the latest and greatest, you'll want a plasma TV with an HDMI input - or the option of adding an HDMI terminal board to your plasma. With a bandwidth of up to 5 Gbps, the HDMI standard allows for transmission of high-quality digital video (up to 1080i) along with up to 8 discrete channels of audio, all on the same cable. Found on the latest HDTV set-top boxes and a growing number of DVD players - many with HDTV-quality upconversion, HDMI has proven more than a home theater fad, and should be around for years to come. Backwards compatibility with the older DVI standard means you can use an adapter cable to use DVI output devices with your HDMI-enabled plasma television.
The 15-pin d-Sub VGA jack is still the standard for PC video connections, and is usually accompanied by a ¼" stereo "mini-jack" for PC audio. If you want to use your plasma as a PC monitor, you'll need a 15-pin VGA terminal or a PC-compatible DVI connection.