Don't understand CSS Absolute and Relative Position

I'm currently learning CSS and I'm stuck in the positioning Relative and Absolute. I understand that these two property are used to define the exact location we want our items to be placed, but however what I don't understand is when we can use Margins and Paddings to define the position of these items, why is there a need still to use Absolute and Relative as it's completely pointless.

A good example I would like to highlight is here http://ift.tt/1OM4MZq... we can just replace position: absolute; with float: right; and it achieves the exact same thing, so what are we still doing with Relative and Absolute position?