Android Orthographic Cameras

The more I look into doing this, the more confused I get. Some people suggest changing the orthographic camera size while some say letter box etc according to aspect ratio.

What I am trying to accomplish is set up my camera so that no matter what resolution, aspect ratio or whatever the phone is, the amount of things seen by my camera is the same. In other words, if I have an object at the edge of a screen and I get a phone with a higher resolution, that object should still be at the edge of the screen and no more space should have come between it and the screen edge than if the app was run on a phone with a low resolution. How can I go about doing this exactly?