The science behind this self watering system for plants Answered

Hi, I was watching a video for a self watering system for plants (link below), and was wondering what the science behind it is called.

I also had a problem where no water came out of the bottle because the hole I made at the bottom was too small. As soon as I unscrewed the cap a little, the water came gushing out.

https://www.youtube.com/watch?v=Ffe7JfYyBFE

Thanks :)