The Bivariate distribution shows the joint probability distribution of two random variables.
Suppose that the position of the center of a hole can vary in both the 'x' and 'y' directions and that the distribution of the center position in both the 'x' and 'y' directions conforms to a normal distribution.
The bivariate probability distribution would be a three dimensional surface showing the probability of the center of a hole being in any position in the x-y plane. This surface would allow you to solve problems such as calculating the probability of a hole center being one standard deviation in 'x' and 2 standard deviations in 'y' from the mean position.
The shape of the surface depends on the standard deviation in the 'x' and 'y' directions, and whether the values of x and y are correlated.