Margin-left is margin, and left is the width, which is a point located at the left of the upper left corner of the box.

Margin-left is the margin, the width margin-left is the left margin, and the distance from the left element.

Left is a point located at the left of the upper left corner of the box.

 

Position: absolute must be added when left and top are used. In fact, left is actually X, top is Y, and the coordinate system expression of all pixels in the browser is (x, y) then, the actual size of the page element is used to calculate the actual left and top values of an element.