https://www.youtube.com/watch?v=FoRUUhb8zgk

1. Symmetric distribution
   the symmetry of the curve around the mean
2 Skewness :
    measure of the asymmetry of the probability distribution of a real-valued random variable about its mean
3. kurtosis:
measure of the tailedness in a PDF (kurtosis-3)
4. standardizing normal variate
 converting all graphs to normal distribution where mean=0 and std dev=1
5.kernel density distribution
 converting the histograms to PDFs
summing the kernels we get height of KDF at that point.kernel is a bell shape curve at that point