Solar radiation from the sun is divided into 3 components: Visible light we can see, infrared we can feel as heat and ultra violet which is invisible but harmful.
The film is constructed from several thin layers of metal and polyester that are bonded together by special adhesives.
When the film is applied to the glass it reacts through absorption and reflection and thereby acts like a filter on your window. Different films have different properties which they absorb and reflect the heat differently but they all carry uv and scratch resistance protection.
As chemistry & technology are advancing the solar window film is too. Higher durability, clearer optics and better heat rejection makes this product very desirable and attractive.