In brief
With position: relative, a positive left value moves an element rightward from its normal position. Its original space remains reserved in the flow.
Useful to know
With position: relative, a positive left value moves an element rightward from its normal position. Its original space remains reserved in the flow. [1]
Therefore, left: 20px is not a substitute for spacing between components. The visual shift can cause overlap without moving a neighbour. To change the layout itself, use a layout rule.
Sources
For further detail and to check the information: