Difficulty to understand how to support multiple screen

Question

I have seen so many questions on StackOverFlow how to support multiple screens. But most of the answers provide this link and this. And in the first one link I have

Answer 1

dp means density independent pixel. When you say for example 300dp means 300 pixels on a medium density (160dpi) screen. So if you want to translate dp on real resolution you have to multiply the dp for the density scale factor: es 300dp are

1. 300 px on a mdpi screen
2. 450 px on a hdpi screen
3. 600 px on a xhdpi screen

so if you specify resources you should remember to use both size and density modifiers a background for a 480x800 px medium screen phone woul be picked from normal-hdpi folder an so on