The content component (com_content) is what you use to write articles.
The content component is extremely flexible and has the largest number of built in views.
Articles can be created and edited from the front end, making content the easiest component to use to create your site content.
When in your site administrator area it is easy to organise your articles into Categories.
Categories can have sub-categories, sub-sub-categories and so on and so forth. The "One-up" category being classed as the "parent". The top category having no parent.
If your site is about, for example cars, you might have an article category for cars:
Your cars category can be sub-divided into the following:
Sub sub-categories might include different models, for example Renault parent category might have sub-categories of:
Each of those sub-categories might have further sub-categories of:
When you create your menu item Cars you can select the option :
Category List - List all categories (shows a list of all the article categories within a category). In the "Select Top Level Category" box, we choose: Cars
So, when your site visitor selects the Cars menu item, your visitor will then see a list: Ford; Vauxhall; BMW; Audi; Peugeot; Renault.
Any sub sub-categories will also be displayed*
* There is a "but" here. When you are in your administrator area, from the administrator menu select : "Content", choose "Categories".
Your list of categories is presented in table format. Near the top-right of your screen is an "Options" button. Click the Options button.
On the Category tab, ensure: Subcategory level, is set to: ALL, and Empty Categories is set to: SHOW. Repeat this for the Categories options: Categories tab