The following is stated in the app listing, hope this helps clarify things for your use case:
By default, continuous auto focus, auto exposure and auto white balance are used across the whole scene. Tapping to focus will switch to auto focus, auto exposure and auto white balance based on that location. The focus timeout setting determines the timeout before it switches back the default mode. The exposure compensation slider on the left allows manually tuning exposure and will automatically adjust shutter speed, aperture and ISO. Further configuration / tuning will be provided in the future.