OIS stands for Optical Image Stabilization, which is a hardware solution that uses a micro-electromechanical system (MEMS) gyroscope to detect movement and adjust the camera system accordingly. OIS is a motor-powered mechanical image stabilization technique that stabilizes the shooting process by sensing a camera shake and repositioning the lens using electromagnets and sensors. It is particularly helpful when taking photos in low-light scenarios as it keeps the camera stable for longer so it can take in more light when in a darker setting, delivering brighter and more pleasing photos that otherwise would likely need a tripod or some other form of stabilization to achieve. OIS is a must-have in modern smartphones, and most mid-range offerings from Samsung, OnePlus, and Google come with OIS on the main camera. If you have to choose between OIS and EIS, it is recommended to pick a camera phone that offers a hardware-based solution, as it is less artificial-looking for video and far more effective for still images.