1.) Using an absolute value means that elements in you page will always be in the same spot, no matter what.

2.) Whichever element is applied recently will be applied on top of other elements but the elements won't force each other out of the way.

3.) The author compares absolute positioning to Velcro because of how absolute positioning sticks elements of a page in place. Glue is another good product for absolute positioning for the exact same reasons.