It’s a bit difficult to display examples of the flex container in use so instead you can see a video below of how the element can be used in WPBakery.
The primary reason for using the flex container is to display items side by side. In the video above I show how you can display a heading on one side and then a button on the opposite side. The flex container could also be used to place 2 buttons side by side. There are various things you can do, it’s up to your imagination!