Terra-Tec H2O is demineralized water as to VDE 0510 and perfect for use with humidifiers and rain systems. It can also be used for aquariums.
Normal water has the problem that the minerals contained in it namely limescale among others, can damage pumps and other units. Also the limestains on glass frames are not nice. Some regions have such hard water that a Super Fog membran can be ruined within a few days. With Terra-Tec H2O you can prevent this problem achieving a long life and longer maintenance intervals for you humidifiers and other devices.
By the way: the claims that demineralized/distilled water is dangerous for humans and animals is wrong. In nature dew is an important water source for animals and it only contains very little minerals. It is simply false that demineralised water deprives the animals of nutrients. Deminderalised water is even sold as premium drinking water for human consumption.