1. What physical pixels?
Physical pixels are small squares on the screen you see. A small square represents a pixel. Of course, the more small squares in a unit area, the higher the number of pixels. This is the physical pixel.
Second, what are css pixels?
The css pixel is actually an abstract concept, not something that really exists, it is relative to the physical pixel.
3. What is the relationship between css pixels and physical pixels? Why is the higher the number of device images, the smaller the picture is?
For example, 1pxcss pixel should occupy 2 pixels. Then in the pixel area of 500x500, a 200pxx200px css picture will occupy 400x400 physical pixels, so if the physical pixel in this area is doubled to become 1000x1000 pixels, then the picture still only accounts for 400x400 pixels, so look Will shrink when the picture is reached