The initials stand for National Television Standards Committee. This is the committee that established the standards for our television system. The problem is that NTSC is an analog system. In computer video, colors and brightness are represented by numbers. But with analog television, everything is just voltages, and voltages are affected by wire length, connectors, heat, cold, video tape, and on and on.
Different countries use different standards.
There is a way to maintain consistency of the television signal. Because everyone sees the world a little differently, we can't just adjust the monitor or the tape player until the picture looks right. This signal is generated by professional video cameras, and by color bar generators. It is laid down at the beginning of tapes so that those tapes can be played back later with accurate color. Color bars are also used to align cameras in multiple camera studios so all the cameras match.