Boxes 1 to 3 are positioned according to the normal flow.

Box 1
Box 2
Box 3

Boxes 2 to 3 are positioned according to the normal flow, but box one has a position attribute with a left value of 300 pixels and a top value of 500 pixels. Because the position is absolute, it doesn't relate to any other elements on the page.

Box 1
Box 2
Box 3

Again, boxes 2 to 3 are positioned according to the normal flow, but box one has a position attribute with a left value of 100 pixels and a top value of 800 pixels. Because the position is absolute, it doesn't relate to any other elements on the page.

Box 1
Box 2
Box 3

Note that the posisitons are all expressed from the left and the top of the viewport. When box 1 is moved, the other boxes move to occupt the space that it created by taking itself out of the normal flow of elements.