P.S. is the easiest way to add important information to the bottom of your site. P.S. is a container block where whatever blocks you put inside of it will be displayed on your site as a popover. The only thing you are limited by is your imagination, all blocks are supported.
My blocks usually start out as problem needing to be solved. When I was working on block garden I really wanted to add an email subscription form to the bottom of my site. Jetpack provides a great form but I couldn’t find the right plugin to help make it into a popover, so I created one.