When you have a float CSS property on a box (with a value different than none ), this box must be laid out according to the float positioning algorithm. Loosely, it says:

if the box has float:left , the box is positioned at the beginning of the line box

, the box is positioned at the beginning of the line box if the box has float:right , the box is positioned at the end of the line box

, the box is positioned at the end of the line box text (and more generally anything within the normal, non-floaty flow) is laid out along the edges of the floating boxes

the clear property changes the floating behaviour.

Anyway, in general you’ll have a better time if you use a flexbox or CSS grid instead of floats, because floats are quirky and have strange edge cases, but if you were ever curious about how the algorithm would choose where to position different floats, here’s a demo (which you can also play with directly on glitch):