This article explains, for those without training in chemistry and physics, the physical picture the scientist has in mind when he uses the word glass . The fundamental concepts of the kinetic theory of matter and models of the three classical states of matter are first presented as background. The nature of the glassy state is then described, emphasizing the random molecular structure of glasses. Comparisons are made of the molecular structure and overall physical characteristics of glasses with those of crystals and liquids. Chemical compositions and the concept of viscosity are also explained.