One of the great things about DSLRs was that the shutter was closed and the mirror was down when you weren’t actively shooting a photo. This meant that when swapping out lenses, your sensor was largely protected from the elements. With mirrorless cameras, though, not so much.
A new Canon patent shows an in-camera mechanism that looks similar to a shutter (but isn’t), that keeps your sensor protected when no lens is attached. What makes it different from closing the actual shutter is that there are no electronics involved in this one. It’s all mechanical and happens automatically as you twist the lens off the camera.