In English I can think of 7 main “question words” that you commonly find at the beginning of a question, indicating a certain type of question.
They are: who, what, which, when, where, why and how. (how is it not whow? - “w” not being its first letter is such an anti-climax at the end of that list, no?)
Verification
(i) You also get questions that reverse the order of a noun and its corresponding verb, such as “are you?” instead of “you are”. Although, of course, “you are?” can be a question on its own when not followed by any more words - unless you want to sound foreign.
(ii) Some questions begin with “Can/could, will/would and shall/should/ought?” - they are alternatives to the above, though verb-specific. “Can” is just “are you able?” and “will” is just “are you willing?”. “Shall” is equivalent to “ought” though from a different word derivation - which is where we get our word “owe” or “own” (be owing). So “shall” is just “are you owing?” in the sense of “are you obliged to do so in return?” Would/could/should are the respective conditional forms.
(iii) The parenthesised sentence near the beginning of this post turns a statement into a question requesting verification in just the same way - just by adding a proposed answer onto the end of a sentence and shoving a question mark after it.
(iv) There are also 1-word questions of verification like “huh?” and “pardon?” - though they are interchangable with any of the main 7.
All the above can be summed up as questions of verification.
What
Turning attention to the main 7, we can whittle them down to fewer:
“Where” can be subsumed by “what”, only with the concentration on spatial location: “what place?”.
“When” can be likewise subsumed by “what”, only with the concentration on temporal location: “what time?”.
“Which” is basically another “what”, though restricted to a particular selection: within which “which one?” = “what one?”.
“Who” is also another “what”, though generally referring to people as distinct from things: “what/which person?”.
Whilst “how” can be subsumed by "what: “in what way?” and “why” can be subsumed as “for what purpose?” I don’t think “what” portrays the movement in “how” and “why”. So we can essentially narrow down questions to verification, “what”, “how” and “why”.
“What” is a question of identification description, “how” is a question of behavioural description and/or explanation, “why” is a question of where that behaviour ends up.
Looked at in this way, there appears to be some kind of systemising “start, process, finish” feel to each of these 3 types of question.
Questions of identification description (what) and behavioural description (how) are generally distinct like noun to verb, static to dynamic, quanta to qualia. Each assumes distinct definition or limits of an object or its quality of behaviour: definite separation between things and degrees/extents.
How
When “how” is being used to request explanation, it is based in questioning “what” goes on (behavioural description) when looked at in a different way.
(a) Spatially (where), objects (whats) can be looked at from different angles, more closely and further away (magnification).
(b) Temporally (when), objects (whats) can be looked at before and after (requiring memory).
If one thing happens consistently before another that happens after, if smaller things are going on at the same time as larger things, “causation” can be called upon - wherein description turns to explanation by connecting descriptions.
(a) If a substance, identified as magnesium, comes into contact with a substance, identified as hydrochloric acid, the reaction can be said to be caused by the smaller atoms of chlorine bonding with with the magnesium atoms, and letting the hydrogen atoms free (looked at from a spatially different, magnified point of view - going on at the same time as the reaction).
(b) If a billiard ball travels toward another, changes its motion once it is next to the other, a sound is heard, and the other changes its motion - these descriptions of identification and behaviour can be turned into explanations by linking the descriptions together. The first ball could be said to cause the second ball to move as it does. And the second ball would be the cause of the first changing direction. Their mutual contact would cause the sound (all looked at from temporally different points of view on the same level of spatial magnification).
Such explanations assume causation, within a spatio-temporal structure - applied to assumed definitely distinct objects of identifiable description.
Why
The question of “why” assumes all of this, taking an identified description (a “what”) as an end-point.
All of the above can be applied to people too ("who"s). A temporally different point of view can identify the description (what) of what was intended by the person before they acted, and connected with the person’s action. Such intensions are taken as the intended end “cause” (the “why” explanation) of any intentional action. Here, the person’s will (a “what”) is identified as the starting condition, and through some process (“how”) or other they arrive at their intentional consequence (“why”). One’s will is the imagined associated consequence, that precedes the real consequence (if successful).
The “why” of this post is to describe how all the many types of question words are tied up with all our understandings and rational structures of the world, and how they assume some combination of definition and causation within a spatio-temporal structure.
When you do so much as to even ask a question, know that you are already assuming many things.