Div Tag information by w3school.com
Wichham's HTML and CSS tutorial about div boxes of position absolute, relative and fixed.
Position: static; is the default where, if it doesn't have any top, right, bottom or left positions, a block element just follows in the order of the code and starts a new line. It isn't usually necessary to state position: static unless you want to cancel one of the other properties. [Inline elements will be on the same line if there is room and position doesn't apply].
1 green icon The silver parent div box is position: relative; so that it flows in the required position in the page text. The parent when position: relative forms the container from which the position: absolute divs take their positions. If the parent containing div did not exist or didn't have position: relative; the position: absolute divs would appear at the top of the screen, taking their positions from the main page container or body of the whole page.
This is Wichham's display
These exercises are not related to the Castro book I am learning from.