This is a new style that has become popular on the web. We have seen it in televisions for a while. If you have watched a DVD in the last five-ten years, you have seen this look.
Now, most of us are using devices and laptops to view media, web site, and some learning content. These screens are not your standard 3:4 ratio. Instead, they are 16:9.
You can immediately see the differences when you look at various monitors. 3:4 is the old school, large monitors and televisions. 16:9 is the newer, more modern televisions, monitors, and mobile devices.
Movies are traditionally 16:9 when you see them in a theatre. When you watch them at home in a non-letterbox format, you lose important pieces of information.