Analog composite video (also called FBAS) is the standard that connects almost all consumer video equipment - television sets, laser disc players, VCRs and camcorders.
Composite video combines the three basic elements of a video picture (color, brightness, and synchronization data) into a single combined composite signal.

Usually composite video is transmitted over 75 ohm cables with BNC connectors. Long video cables are prone to signal loss and RF interference. The 75 ohm cable chain must be terminated at both ends.

The analog S-Video (also called Y/C) signal separates color and brightness into two separate channels on two separate cables. This makes for a sharper picture image, with less granularity, on the receiving device. The luminance signal contains brightness, intensity, and signal timing information. This signal contains all picture information except for color. The chrominance signal contains only the color information.
By feeding only the luminance signal into a monitor the complete black and white image can be seen.
S-Video for consumer devices is carried on cables that end in 4-pin Mini-DIN connectors. These cables are made up of two separate small cables in one jacket. In professional installations S-Video is mostly carried on two separate cables with BNC connectors.
The term S-VHS is often used, it is not a video transmission format, rather it is a tape format which is almost always used in decks that support the S-Video signal standard. These two terms, S-VHS and S-Video, are often used interchangeably to refer to S-Video.

Analog component video contains three feeds. The luminance signal (Y) contains the black & white (brightness) information from the original RGB signal. The color difference signal B-Y (PB) contains the blue information, minus the luminance information. The color difference signal R-Y (PR) contains the red information minus the luminance information. In the display device the three channels are recombined to produce a full color picture, recreating the green information within this process.

The analog RGB signal is carried over three, four or five lines (depending on the sync characteristics). Three lines carry the color information for the red, green and blue components: R,G,B. Each of the three channels R, G and B include the color signal and the luminance information.
The sync signal can be provided as sync on green RGsB, one combined sync signal RGBS, separate sync signal for horizontal and vertical RGBHV or sync on all three RsGsBs. For fully separated sync transmission five individual channels (cables) are used and the H and V channels carry the horizontal and vertical synchronization. RGB video signals and RGB computer grphics signals have some significant differences and are not compatible without a scaling unit!

Viewing any of the three channels of a RGB transmission separately, a black and white image is always visible, because the Y information is included in all three channels. This is a large wast of bandwidth, because actually the same signal is carried three times.

By using just one channel for the luminance information and two channels for the color information, bandwidth can be saved drastically by carrying the same information.
Component video YPrPb (YUV) consists of three signals. The first is the luminance signal, which indicates brightness or black and white information that is contained in the original RGB signal. Monochrome signals contain only intensity luminance information, also called luma. It is referred to as the Y component. The apostrophe indicates that the component is gamma corrected.
The second and third signals are called 'color difference' signals which indicate how much blue and red there is relative to luminance. The blue component is B-Y and the red component is R-Y. The color difference signals are mathematical derivatives of the RGB signal.

When color information is added to the video signal, the luma signal is left intact for compatibility with existing equipment, and two color information components are added. They are called U' and V'.
Y'Pr'Pb' (Y'U'V') signals are matrixed components. The luminance Y signal is derived from the Red, Green, and Blue components by the formula 30% Red, 59% Green, and 11% Blue. The R-Y signal (Pr) is derived by subtracting this luminance signal from the Red signal. The resulting signal contains only color difference component for red.
The B-Y or Pb signal is derived by subtracting the Y signal from the blue signal to get the color component of blue. A G-Y component for green is not needed because all information is carried with the Y signal and the red and blue color component.

The color components are also called color difference signals. The U' component is the difference between blue and luma and the V' component is the difference between red and luma.

The reason to use YPrPb instead of RGB is the large amount of saved bandwidth. In the RGB signal the luminance component is carried three times. Typically, the color components are about half the bandwidth of the luminance component. Therefore about 4 Mhz of the necessary RGB bandwidth of about 12 Mhz can be saved.
The luminance image (Y) will usually be transmitted 25 or 30 times per second, while the two difference signals will alternate at half that rate.
In the receiving unit the signal is matrixed and the original information is available again.

Y is luminance, U and V are the color differences: U = R-Y, V = B-Y

Sometimes there is confusion about connecting a YUV source (DVD player) to a tv-/plasma-/whatsoever-monitor or a projector. Both can be handled on the DB-15 connector, but the signal formats are different.
A 'conversion cable' can be used to connect the YUV source on the DVD player to the DB-15 input on the display device, but this display device must have the input format switching between RGB and YUV. This cannot be switched automatically, connecting YUV to RGB will result in a green picture.
RGB is expecting and displaying red, green and blue, component video is transmitting red minus Y, Y and blue minus Y. Thus from the red cable it gets zero red, from the green cable it gets the green signal from the full spectrum of the Y signal and from the blue cable it gets zero blue signal, the only data it has to display is green.

NTSC stands for National Television Standards Committee. It is the video transmission standard for North and Central America, including Mexico and Canada, and Japan. Its technical format is 525 lines per frame with roughly 30 fps (frames per second) refresh rate. It is pretty much synonymous with composite video when talking about a video signal, but is not necessarily equivalent to the output from a video capture card that may claim to be NTSC-legal.

PAL (Phase Alteration Line) is the European counterpart to the NTSC standard. It has a higher vertical resolution (625 lines per frame) but a lower refresh rate (25 frames per second) that can cause flickering. It is the standard for the UK, Western Europe, the Middle East, and parts of Africa and South America.

SECAM (Systeme Electronic Pour Couleur Avec Memoire) is very similar to PAL. It specifies the same number of scan lines and frames per second, but differs in that chrominance (color) is FM modulated. It is the broadcast standard for France, Russia, and parts of Africa and Eastern Europe.