Shot Size

Wide shot:

In the wide shot, the subject takes up the full frame. In this case, the girl's feet are almost at the bottom of frame, and her head is almost at the top. Obviously the subject doesn't take up the whole width and height of the frame, since this is as close as we can get without losing any part of her. The small amount of room above and below the subject can be thought of as safety room — you don't want to be cutting the top of the head off. It would also look uncomfortable if her feet and head were exactly at the top and bottom of frame.

Mid Shot:

The mid shot shows some part of the subject in more detail, whilst still showing enough for the audience to feel as if they were looking at the whole subject. In fact, this is an approximation of how you would see a person "in the flesh" if you were having a casual conversation. You wouldn't be paying any attention to their lower body, so that part of the picture is unnecessary.

Medium close up:

he medium closeup is half way between a mid shot and a close up. This shot shows the face more clearly, without getting uncomfortably close.

Close up:

In the closeup shot, a certain feature or part of the subject takes up most of the frame. A close up of a person usually means a close up of their face (unless specified otherwise).

Close-ups are obviously useful for showing detail and can also be used as a cut in.

A close-up of a person emphasizes their emotional state. Whereas a mid shot or wide shot is more appropriate for delivering facts and general information, a close-up exaggerates facial expressions which convey emotion. The viewer is drawn into the subject's personal space and shares their feelings.