How does android let you change the phone interface without confusion?

I don’t know the explanation here, because the video link I’m going to post below is very clear. This teacher is really good. If you have time, you can watch his whole set of videos.
The link is as follows:
Let your android layout have good adaptability https://www.bilibili.com/video/BV1w4411t7UQ?p=4
I will briefly talk about what the teacher used, which is the auxiliary line used Control the layout. as the picture shows.

For specific details, you can see the video link above, I won’t make any trouble here.