Relative position moves an elements in relation to it's normal flow. You do this with the offset properties of top, bottom, right or left to indicate how far you want the element to move. (Without the offset, the element won't look any different than it normally would.) The surrounding elements will not be affected by this change. They will stay in their normal places.
These are the same three divs as before. But the orange div has been moved with relative positioning. Notice that the space where the orange div was is maintained.