How does category search work in wordpress?

Question

Search engines

Friends - tell me, maybe someone came across this on WP.
I have headings and categories.
There are posts that belong to - headings and categories.
There is a search for "standard" - from the "standard topic", it works - the posts are found without problems ...
But when I want to search for posts by category, it doesn't find anything ...
It's by the category ...
I know that you can track if there are filters query in "input_e" search , and then make it search in categories that you can pre-specify.
But then, as far as I understand, "search" will give results only from categories ...
And then, it will either be snares for "posts", or "snares on categories" ( in principle, sometimes it is useful ).
But there is a method that can search for everything...