The name "Phase Alternating Line" describes the way that part of the colour information on the video signal is reversed in phase with each line, which automatically corrects phase errors in the transmission of the signal. NTSC receivers have a tint control to perform the correction manually. Some engineers jokingly expand NTSC to "Never Twice the Same Colour" while referring to PAL as "Perfect At Last" or "Peace At Last"! However, the alternation of colour information - Hanover bars - can lead to picture grain on pictures with extreme phase errors.
The PAL colour system is usually used with a video format that has 625 lines per frame and a refresh rate of 25 frames per second, interlaced, such as systems B, G, H, I, and N (see broadcast television systems for the technical details of each format). Some countries in Eastern Europe which formerly used SECAM with systems D and K have switched to PAL while leaving other aspects of their video system the same. (However, some other countries changed completely from SECAM-D/K to PAL-B/G.) In Brazil, PAL is used in conjunction with the 525 line, 29.97 frame/s system M (other countries using system M use NTSC).
Recently-manufactured television receivers can typically decode all of these systems, except in some cases PAL-M.
When video is transmitted baseband, most of the differences between systems are no longer significant, other than vertical resolution and frame rate, and in that context, unqualified PAL invariably means 625 lines at 25 frames per second, interlaced, with PAL color.