The Samsung Galaxy Note 8 is the first phone to offer dual OIS for its dual cameras. This means that both the wide-angle lens and the telephoto lens have an optical image stabilization (OIS). The helps improve the the low-light performance as well as help stabilize images and videos. The reason why the OIS improved low-light performance is because it allows the camera to capture shots at slower shutter speeds, while still maintaining a sharp-looking image. For videos, the OIS helps to minimize shakiness caused by hand movements when shooting hand-held, what most of us do of course.
If you check other dual camera setups on other phones, you can see that the second telephoto lens lack OIS and it's only the wide-angle lens that has one. It's great to see Samsung improving over previous offerings and pushing this great dual-camera configurations forward with better and more advanced features.
Here is a video by PCWorldVideos that highlights the Note8 dual camera features and talks about the dual OIS as well and its importance.
The OIS becomes even more important when shooting with a telephoto lens. The recommended shutter speed according to the shutter speed rule of thumb is that you need to make sure that the shutter speed matches or exceeds the focal length of the lens. So if you are shooting with a 77mm lens, you should shoot with at least 1/77s shutter speed or faster to make sure you get a sharp image. This is why most interchangeable telephoto lenses for DSLR cameras have lens-shift OIS built-in the lens. I personally care about OIS because it really helps improve the low light performance, so I can shoot images in less ideal lighting conditions and come home with some great night shots.
This is one of the most noticeable advantages in the Galaxy Note8 camera section - well done Samsung!