Focussing on a near point throws the areas behind it out of focus. When focussing on a further point, although the near areas are out of focus, the range of in-focus areas is greater. In the above images a large aperture (f1.8) empasisies the effect.
The point of focus affects the composition by directing attention to the clearer areas. Unfocussed foreground is generally less appealing than the converse, but it can be used to good effect.