The time for which the shutter of a camera remains open is called its shutter speed. When the shutter remains open, it allows light to enter through the camera. Light is received by the sensors, which then transmit it for processing and production of the image.
If you intend to click pictures with your GoPro, the Protune feature allows you to juggle between fast and slow shutter speeds. You can use a fast shutter speed when clicking pictures of high-speed action in well-lit outdoor conditions.
Moreover, if you want to click pictures in a backdrop like the night sky, for instance, you can switch to slower shutter speeds.
The Protune feature also allows you to alter shutter speeds for video recording. Here, the shutter speed is a multiple of the Frame Rate (FPS). It means that if you shoot at 60 FPS, you get to choose shutter speeds like 1/120, which are multiples of 60.