A search used to end with a list. A person read ten titles, chose one, and arrived somewhere. Answer Engine Optimization deals with what happens now that the answer is written on the result page itself, from material taken out of pages that the person may never open.
That shift moves the target. Being placed in a list and being used as a source are two different achievements, measured differently and earned differently. A page can hold the first position for a query and be named in none of the answers generated for it.
The field has its own vocabulary, its own failure modes and its own measurements. Formatting decides whether a page can be used at all. What the page carries beyond the agreed knowledge decides whether it is worth using. And accuracy, attribution and authorship decide whether the answer built from it can be trusted, which is where the consequences sit on subjects that matter.
Each subject below states what is settled, names what the widespread advice leaves out, and answers the questions that come up in practice.