In simple terms, condensation is when humidity in the air and a cold surface come into contact, turning gas into liquid, i.e. the water we can see forming on the windows.
Products currently available in the North American market suffer the most, even including Energy Star approved windows, where condensation continues to be an issue. The separation between the indoors and outdoors is greatly compromised, and the indoor panels are almost as cold as the outdoor panels, leading to severe condensation.
High performing windows like Internorm, allow the cold air to stay on the outdoor panel and the indoor panels to stay warm, therefore limiting any condensation.