Glass panes common in the walls of buildings, especially sky scrapers, allowing people inside to see the outside and to let light in.
Windows have been around for thousands of years, although they were originally just holes in the walls of buildings, without any glass panes.
Windows should not be confused with the remarkably unstable and virus-susceptible Windoze
Yesterday, I was wondering if it was raining or not, so I looked outside through the windows and saw that it was, in fact, raining. Without my windows, I could have gotten wet.