Here's a quick example

Now, each row corresponds to what's called the coefficients of a binomial expansion of the form (x+y)^n,where n is the number of the row,and we start counting from zero.So if you make n=2 and expand it,you get (x^2) + 2xy + (y^2).The coefficients, or numbers in front of the variables,are the same as the numbers in that row of Pascal's Triangle.