A raw display is like a TV screen, but it doesn't have any fancy stuff going on like colors or pictures. It just shows what it's given, like when you draw on a piece of paper with a pencil.
Raw displays are useful because they can show things like text or simple images without needing a computer to tell them what to do. They can also be used in things like alarm clocks or thermostats, where you just need basic information displayed.
However, raw displays aren't as fun to look at as the displays on our phones and tablets because they can't show fancy things like videos or complex images. They're like the old-fashioned TV screens your grandparents might have used.
But sometimes simple is better, and raw displays serve an important purpose in many different devices.