In the category list, if a parent category is selected to filter post, the list produce will include post of all sub directories that the user has authority to see.

I was expecting the Mother category link only to show those posts directly inside it.

Ok this maybe how it works.

You give each post a tag or two or three and if you click on one of them it lists all post that carry that tag.

Going to try and do a few on Blood and Wine.

Tags only link Posts to Posts, so although they can be added to pages, they do nothing???

They only link within the same Blog. There is a plugin that links to wikipeadia.

So it's possible to link to a search engine.

Tags work on Posts but not Pages??

What is a Tag

[2.4.x] Any way to change "tags" to SEARCH Automat