An ActionCam consists of 2 main components – Lens + Sensor. Lens is an assembly of multiple optical glasses used with a camera body & mechanism to make images of objects. An image sensor takes light and converts it to a digital format which the camera can wrangle into a photo. Sensors are usually rated in terms of their size (diameter) and megapixel capacity. ⠀
The quality of lens & sensor determines the output quality of the image or the video. In simple words to get good quality image/video you need to have a good quality lens & sensor.