Am I right about the screen resolution for Android?

Question

User interface

I looked through a lot of information, but I could not find anything intelligible. Probably not looking well :)
Can someone answer how to choose the right screen resolution when developing a game for Android. In the project, I set this resolution. I think it is standard for smartphones. But the black bars on the sides confuse me.
How will this resolution behave on smartphone screens? And on a tablet in portrait orientation? The camera preview seems to show an adequate picture
But still, how to do all this correctly. I'm really trying to get into it, but I can't do without someone's help.