Relationship between floating elements and parent and brother boxes

1、 The relationship between floating element and parent box
● The floating of the child box is aligned with the parent box
● Does not overlap the parent box , And it won't exceed the inside margin of the parent box
2、 The relationship between floating elements and brother boxes
In a parent box , If the previous brother box is ：
● floating , Then the front box will align with the top of the previous box
● Ordinary flow , Then the current box will be displayed below the previous box