Here's my attempt at a layman summary, adapted from this answer.
When we talk about communication happening "at 24 GHz", we're referring to a small range of frequencies. In order for the signal "at 24 GHz" not to trample all over the signals at all the other frequencies, there's a hard limit on how much the signal is allowed to differ from a 24 GHz sinewave.
The whole point of having a radio "band" is that by placing a limit on how much the signal can differ to a sinewave, it becomes possible to create filters which remove signals that differ too much from your sinewave, thus suppressing them and keeping only the signal you're interested in.
For example, here is random noise filtered to contain only frequencies between 190 Hz and 210 Hz:
Observe that it is not that far off from a (200 Hz) sinewave. For comparison, here's noise filtered to contain 150 Hz to 250 Hz:
Note how it differs much more from a perfect sinewave. Now, if you take a 24 GHz sinewave and start arbitrarily turning bits of it on and off, the receiver will not see it the way you send it, because turning bits on/off arbitrarily will make the signal fall outside of the 24 GHz range. The receiver will filter out frequencies outside the 24 GHz range, thus distorting the signal. Bottom line is: if you modulate the signal naively by turning bits on and off, it won't work with the idea of filtering out unwanted frequencies.
Before filtering, the above signal looked like this:
Think of it as what a radio receiver sees before it filters out unwanted frequencies. I think that's a reasonable layman approximation. Note that the horizontal scale here is exactly the same as in the images above – what you're seeing are all the frequencies higher than 200-odd Hz. Frequencies below 200 Hz are also there, but they are not obvious to the naked eye.
(the math works the same at Hz or GHz scales, so don't let this put you off)