Point of view in photography simply means the position from which the camera sees the scene. Are you looking down on the subject? Are you looking up at the subject? How close are you to the subject? Is there anything between you and the subject? Every decision you make about point of view will change how your viewer sees the photo.
Regardless of what point of view you chose when taking a photo, remember the power of juxtaposition.
Shooting a subject from an "unexpected" angle will have more impact than the viewing angle encountered in every day life.
For example, looking up at an ant will have much more visual impact than looking down on an ant. Or an eye-level shot of a bird is much more powerful than looking up at a bird in a tree.
Becoming the Subject
A powerful point of view involves "becoming the subject." This means that you shoot the photo from the angle of the subject. For example, a shot of surgery shown as though you were looking through the surgeon's eyes (patient and surgeon's hands visible but not the surgeon's face/body). These shots allow the viewer to feel like they are experiencing the event first hand.
Shooting From Eye Level
Shooting a photo from eye level of the subject is the quickest way to help your viewers connect emotionally with a photo subject. By literally putting them at the photo subjects level, you create an instinctual response.
When we are at eye level with a subject, we personify that subject—even if it is not human.
Shooting at eye level also allows you to see more of the subject than shooting downward or upward (or even from the side) would allow. This straight-on angle also helps to prevent distortion caused by perspective or angle of view.
Shooting from Below
When you shoot a photo from below a subject, you can make the viewer feel as though the subject is in control of a situation. The simple act of looking up at a subject can impart a feeling of smallness, loss of control or a sense that the subject (or object) is unobtainable.
This has been used in real world situations throughout history. For example, thrones are set higher than other chairs, judges sit on a podium and executive desks are just a bit taller than normal desks.
A severely low shooting angle can also give the illusion of being inside the frame of the photograph.
Like almost everything in photography, this goes back to our instinctual reactions to situations. In a forest of tall trees we feel small when looking up. As a child we must obey our larger parents. Shooting with an upwards angle allows us to tap into this instinctive response.
Shooting from Above
Shooting from above a subject allows the viewer to feel superior to the subject or convey a sense of protectiveness of the subject.
It can also give the viewer the impression that they are the object of the attention of the subject in the photo, as though it was the viewer placed on a stage. If the stage level effect is achieved, the viewer will often feel adversarial towards the subject.