The binomial distribution is a type of discrete probability distribution. It shows the probability of getting 'd' successes in a sample of 'n' taken from an 'infinite' population where the probability of a success is 'p'.
(note the similarity to the normal distribution)
The binomial distribution would be appropriate if items taken from a process were inspected. If the proportion of defective items is 'p' then the binomial distribution gives the probability of finding 'd' defectives in a sample of 'n':