Well, the joke was that SECAM stands for System Essentially Contrary to the American Method....:-)
The basic, oversimplified description of the three common encoding methods is as follows:
NTSC: Used in North America, Japan, and a few other areas. Luminance ("black and white" information) is sent just as it was before color, and color information is provided in two "color difference" signals (actually, derived along with the luminance (Y) signal) via matrix multiplication) which are carried on a "color subcarrier". The chroma (color) signals are severely band-limited compared to the luminance signal, which is one reason you can never fully recover proper RGB from an NTSC-encoded signal. The color information itself is encoded such that the PHASE of the chroma signals, relative to the reference signal, is important in recovering the color. As used in the U.S., the broadcast standard provides a line rate of approx. 15,734.26 Hz, and a field rate of 59.94+ Hz*
PAL: Very similar to NTSC, with the exception that the phase of the color subcarrier is reversed on alternate lines; this tends to cancel some of the more common color errors seen in the NTSC system. (The color signals of PAL are also simple color-difference signals, rather than using the more involved RGB -> YIQ matrix of NTSC). In the most common European PAL broadcast systems, a line rate of 15,625 Hz and a field rate of 50.00 Hs are used*.
SECAM: This system is very different from both NTSC and PAL. Luminance and color-difference signals are still used, but the color difference signals are sent separately, on successive lines. This requires at least a one-line memory or delay line be provided in the receiver for proper color decoding. The broadcast SECAM systems usually use similar line/field rates as for the PAL broadcast standards noted above*.
Note: In all three cases, the terms "NTSC", "PAL", and "SECAM" technically refer only to the COLOR-ENCODING systems described above; they do not specifically imply a set of timing standards or frequencies. The one possible exception to this is the use of the term "NTSC", since the U.S. National Television Standards Committee ALSO came up with various timing standards for U.S. television. But in all cases, the color encoding method is not STRONGLY tied to a specific line/field timing. For example, there is at least one broadcast system (Brazil's) which uses NTSC encoding, but at the line/field rates more commonly seen in the European systems.