"DOF" is short for Depth of Field which is a measure of focus. When you have shallow depth of field, a select item in frame will be in focus, and the objects closer to and further away from it will be blurry. Different lenses and focal lenghts will yeild different DOF levels, because of how much light is let in at a certain aperture.
Holy crap, that girl is HOT! Oh yeah, the video was real nice too! Top-notch lighting. Looked like 35mm film if I didn't know better. Did you DP that? That was probably the best-looking HVX200 footage I've ever seen!