Well put simply, CREASE takes the voltage above zero and offsets it below, and the voltage below zero gets offset above—this causes sharp discontinuities (which are depicted on the front panel) that can be used as triggers (as @mdoudoroff points out, they’re not necessarily triggers that all modules will accept, so requires some experimentation). Sometimes, with nothing patched, if I want a manual trigger I will plug crease to something and simply turn survey past zero.
@desolationjones 's version of using crease this way is interesting because it uses FADE’s inversion at RIGHT output to give you the difference between two signals. This can maybe be understood more easily in audio terms because this is also how you get mid-side decoding out of Cold Mac—plugging stereo audio signals to FADE and OFFSET gives you FADE + OFFSET (mid) at LEFT output, and FADE - OFFSET (side) at RIGHT output. Maybe it’s more confusing to put it in audio terms but I’ve found that the easiest way of understanding the relationship between there.
As far as the AND and OR circuits I think the drawings in the technical maps are the easiest way to understand those, but I realized you can’t create gates or triggers out of nothing with those, it’s more a case of gate/trigger manipulation, because you’re not doing anything to manipulate the rising edge other than whatever rising edge you’re putting into the circuit… A sine wave in there with SURVEY at noon will give you discontinuities, but I don’t think they’d trigger anything that wouldn’t be triggered by the sine wave alone…