The quantise filter is a close relative of the clip filter, in almost every respect the operation is the same, except that the number of "steps" within the filter can be set using the "c" input on the filter control. Quantisation removes any smoothness from filtered transitions, making it somewhat unfriendly towards any bump that might be present. An in depth understanding of this filter is not essential while learning the Deep Texture Editor (DTE), simply to be aware of what it does and that it works like the clip filters will be enough. Armed with at least a passing awareness of the less common filters will mean when the time comes, you will know what filter you need to employ and not be left floundering in ignorance. Quantise is powerful, but not likely to be called upon all that frequently.