Sticky Flexbox Footer Example
This is the "Sticky Footer" Example. If there isn't enough content on the page to fill the height of one screen depth, the footer will always remain "stuck" to the bottom of the browser window.
Once there's enough content, the footer just moves down into the next screen depth, and so on, and so on.
If you're on a big monitor, or possibly a laptop, try making the browser window "less" deep and see how the footer responds to the content above it.