In here you can get them on every street corner.
I guess they are not common in USA, maybe typical dutch?
they are pots with a drainage system inside.
the idea is that you can't overwater, that the water flows away in a resevoir at the bottom, so that the roots don't stay wet.
they are made of somekind grinded stone and somekind plastic.
so they are light and very strong and cost about the same as a regular pot.
here is a youtube video about it with a horrible dutch accent