The value is the numerical part of the measurement. The precision indicates the confidence we have in the value. If you learn only one thing from this course, it should be unit factor analysis. Each one of these factors comes from an equality. For example 12 inches equals one foot.
All unit factors equal one, which is why they are called unit factors.
The powerful thing is that you can always multiply by one without changing the value of the thing you multiplied. You can multiply by one over and over, no problem. Unit Factor Analysis uses this fact as the basis for what it does. Certain prefixes imply unit factors. You can, for example, have the unit mm which is millimeter.