The binomial distribution describes the number of successes in n independent trials, each with the same probability of success p. It is written B(n, p), with expected value n x p. It models, for example, the number of customers who buy within a group that was solicited.
Example
from scipy.stats import binom
binom.pmf(3, n=10, p=0.2) # P(exactly 3 successes)