Action cameras are dedicated camera systems which are designed to record a fast action, sports, and stunts while being attached to the person performing the stunt or mounted on a vehicle, board or drone.
The best thing about these cameras is that they are capable of recording in-camera 4K videos which is something that even not many proper DSLR cameras can achieve at this point.
Plus, the unwieldy nature of DSLRs and mirrorless systems means these cameras are rarely suitable for action sports and stunts. Especially, where the camera has to be worn by the performer or be exposed to tough terrain or the elements.
Off late a handful of Chinese manufacturers have started to chip away GoPro’s stranglehold in the market by launching their own cameras.