If you click on the green "more info" link below the photo, it will take you to another page that has a link the online source for this item. You should be able to get further information there.

These particular plants are Tillandsia (air plants); part of the bromeliad family. Many are about 4-6", which will give you an idea of the size of these planters. The air plants don't need soil and work great in planters like these. To answer your question, I'd say BOTH because you could also grow small cacti or mosses in them with the proper substrates. I've also seen them with tealight candles. (I'd use electric tealights due to concerns about heat, though.) :-)

These are live plants that survive without soil