CDF is the definite integral of PDF. CDF is cumulative distribution function and PDF is probability density function. In other words, CDF represents the probability that a random variable is less than or equal to a certain value, and PDF represents the probability density of a random variable near a certain value. Mathematically, it can be expressed by the following formula: CDF (x) = ∫ _ {-∞} xpdf (t) dt, PDF(x)=d/dxCDF(x).