PAL

The Phase Alternating Line (PAL) specification describes the analog television system for Europe (and other countries - see map). Although not used for modern digital television, it influences still-current standards such DVD. Its two most important characteristics (for our purposes) were its frame rate and color format.

• PAL-type video consists of 25 interlaced frames of video per second. In the original analog standard, each frame consisted of 625 scan lines, 576 of which were visible. The remainder was used for vertical synchronization and other purposes. Each frame was composed of two fields; each field therefore consisted of 312.5 scan lines. See interlaced fieldbased for more about interlaced video.
• PAL's color is governed by Rec601 (also known as 'Rec.601,' 'BT.601' and 'SMPTE 170M'), which is an international standard that describes color conversion between the RGB color format (as it is taken at the camera and displayed on the screen) and a particular YUV format, which carries the internal signal. See Colorimetry for more on this and related standards.

External links

wikipedia:PAL (from which this summary was adapted)
Video Basics (doom9.net) An illustrated guide for beginners.