I always though of a "channel" as a collection of frequencies, or a frequency range, packaged together for easy reference. IE channel 60 for us is really 72.985Mhz-72.995Mhz, meaning your radio is working in that range, and anything else in that range could be considered "on your channel" and likely to mess with your signal. It's not a technical definition, but it works.

Frequency, of course is the number of cycles per second of the waveform.

Channel in reference to control functon on our systems, ie, a "6 channel radio" is, in fact, annoying. I suspect the usage started back in the reed days, when differnet control functions were, in fact, on different frequencies, as I understand it (before my time, that's based on stuff I've read). But it's still an annoying nameing convention.

Lucky for us, the most "channels" you see on one radio is 10 (normally), and the lowest 72Mhz channel number is 11. So, there's no danger of your 6-channel radio on channel 5 interfering iwth the 4 channel radio on channel 2, but not the 3 chanel sytem on channel 6.