It’s a harmless, colorless gas. It sits between the dual panes and the insulated glass. It also contains no moisture. What it does is slow the transfer of heat through the window. Gases like argon are better than regular air because air has moisture that can condense on the inside of your glass, and that makes your window cloudy. Air also insulates less than argon gas. It’s a really smart buy with no downsides. It also reflects a unique variety of colors depending on what’s in front of that window.