This window is used to place html-formatted text into any zone. You don't need to know HTML to put the text in. However, placing images or complex elements will need such knowledge. You can also use this window to place HTML-code of counter, soclal-media widgets etc. on your page.
Example of HTML-formatted text is shown below.
There are many presets to show your article list. But if you don't like any of those - you can always create your own by selecting the "According to template" option in the Image tab of your article list (Article list > Image position > According to template). You do need to know some html and css to do that though.