What is Terra Aqua Column?

A terra aqua column is made of two 2 liter bottles connected together. The top bottle is upside down with the cap facing downwards which contains a terrarium including soil, plants, etc. There's a string from the soil to the terrarium that dips into the water of the aquarium through the cap. The aquarium is set right underneath the terrarium holding it in place. The aquarium holds plants, gravel/soil and aquatic life like freshwater snails or fish... *But you should google it or go to bottle Biology.com? for reference... -_-