Like any other filter, this one protects the front lens from water splashes. 

This particular model of adapter allows you to use lenses which do not have a dedicated aperture ring. These adapters do not have any electronic connection to the camera and hence cannot "tell" the camera what aperture is set, therefore the adjustable ring on the adapter provides a means of manually adjusting the amount of light passing through the lens to the camera sensor. NB If you have lenses WITH an aperture ring you could use another simpler (and cheaper} model of adapter and manually adjust the aperture on the lens. 

Black soft filters can be used to reduce blemishes and wrinkles in people or objects by reducing the resolution of the image. They can also be used to increase contrast and create a halo or glow effect for specular light sources in a scene 

I have used one on a Sony a7 mkii. 

You could try this tip. Hope it helps. Pan&tilt operation: Press the “pan/tilt” button on the upper right corner (A direction icon will appear in the middle of the screen when you press the “pan/tilt” button) →use the sound and brightness buttons to move the lens(The specific operation is shown in the video).