Skewness is a measure of symmetry. A skewness close to 0 means that the distribution is symmetric. A
negative skewness means the distribution is skewed to the left (the bulk of the histogram is to the right), a positive that is is skewed to the
right (the bulk of the histogram is to the left).
Since the normal distribution is symmetric, a normally distributed sample should have a skewness close to 0.
Kurtosis is a measurement about the extremities (tails) of the distribution. The normal distribution
has a kurtosis of 0, so a normally distributed sample should also have a kurtosis close to 0.