Answer
The second law is a fundamental law because it applies to everything in nature, decreeing that everything tends toward disorder. It is not an "exact" law because it is "only" a statement of probability.
For example, there is a nonzero chance that 100 pennies rolling off a table will all land on edge, arranged in a uniform 10x10 grid. The second law does not forbid this from happening, but merely states that it is highly improbable.
