How does the interactive font preview feature work in Adobe Illustrator CC 2017?

Question

Adobe Illustrator

To use the interactive preview feature, select the text and hover over the font list. Place the loaded text in a container, or fill the container with alt text to visualize your project more accurately. Now it's even easier to work with typography objects that have the same font family but different styles (and vice versa).
I read the description but I can't figure it out myself. Can you tell with examples?

Answer 1

Here is what is meant:
PS Of course Adobe translators should be fired. I went to the English version of the page to understand what is written there.