Focus (and the related depth of field) can completely change the look and feel of a photo. Recently I took a walk in the Shakespeare Garden in Central Park. I generally take macro shots of flowers. As you can see above, you don’t get much in focus (there’s a shallow depth of field) in macro photography. This can be a challenge, but it can also produce a great photo because your eye is drawn to the sharp, in focus, flower and away from the blurred background.
You can get similar effects with middle range depths of field in a wider shot. Here the same purple flowers are in focus, but now instead of one flower, it’s the whole plant. And now you see much more of the background, including what appear to be roses.
Finally, here is the widest shot with the largest depth of field–and nearly everything in focus. Again you can see the purple flowers, but here they aren’t the main feature. Your eye isn’t as drawn to them (although I did rather obey the rule of thirds, so your eye probably will go to them a bit.) But for me the path is the first thing I notice and the shock of pink roses. Even though the roses are farther away than they were in the middle photo, they are sharper and more clearly roses (rather than some other type of pink flower). Three photos of the same plant; all so different, all with their different depths of field and focus.