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. 

You can attach a phone to it but it is mainly a desk based lamp. You might be able to walk around with it but it would be a bit clumsy I think. 

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 

Can be used while charging, built-in 1000mAh rechargeable lithium battery.  

Please refer to this video https://youtu.be/QTqaGuu7kVM.