So that's my coin. And let's say on a given flip of that coin, the probability that I get heads is 0.6, and the probability that I get tails, well, it would be one minus 0.6, or 0.4. And what I'm going to do is I'm going to define a random variable X as being equal to the number of heads after 10 flips of my coin. Now what makes this a binomial variable? Well, one of the first conditions that's often given for a binomial variable is that it's made up of a finite number of independent trials. So it's made up, made up of independent, independent trials. Now what do I mean by independent trials?