standard box
box-sizing:context-box;The size of the standard box itself=content+border+padding
The size of the standard box in the page = content+border+padding+margin
Adding border, border, and margin to a standard box will open the box
weird box
box-sizing:border-box;The size of the weird box itself = content (including padding, border)
The size of the weird box on the page = content (including border, padding) + margin
Adding border and padding to the weird box will not open the box, but will only reduce the size of the content