The best visualization of that feature is this manual or a glossary. You may see in action just by exploring this manual deeply. Below will find a bit about administration panel.
Category is main unit of the knowledgebase. There is possibility to use only categories but if you will add atricles as well you may add relation of those. 

Knowlegebase is disable by default. To enable it just open administration panel >> Settings >> Content >> Knowledgebase tab.

Knowledgebase category

Click button to add category, the best if you will add two to see how that is working at the system. Below the most important part of the category, like name and description. Parent category is responsible for showing a 'tree'. Currently would like to add just a top one so just click save. 

My two knowledgebase categories are ready. 

Need to add a bit more, will add to each category a two categories more. When added, and at the public store will click on any, a tree will be shown. 

Knowledgebase article

Article has some advantages over categories, but are not vissible under the tree view. To avoid mistakes when connect category and article, you may simply open category and click article tab. This way when adding a new atricle, a parent category will be added automatically. What I need to do is add title and content. It is worth to consider if would you like to add possibility to leave a comment. There is a setting on this screen.

Need to add a two more, so will be able to show the advantages. When click save on the screen above, will return to parent category, where will be able to add two article more. 

Now need to open each article from this category, as would like to 'link' those between each other. So will open the first article and click 'Related atricles'

It is easy now, as have only 3 atricles. Click all 3. Note, first step atricle is clicked as well.

Adding action remove self assigned atricles. Do not need to bother you with exluding atricles to avoid a loop.

How that is presented at the public store?

First what you are able to see is a list of atricles linked with the category. It is done automatically when you be adding an article via the category view or will check parent manually. If will click to open step one, will be able to see a content of this atricle, list of related atricles and comment box - for the fist atricle I have checked option for comment to show how it is displayed. 

If will click any other article, will see only content. That is because I have not added related atricles to the rest. Need to do this manually, for any sigle article. At this step, comment checkbox was unchecked, so there is not field for type a comment.