Continuous Random Variable
In the probability distribution the sum of all the probabilities was 1.
Consider the variable X denoting "Volume poured into a 100cc cup from coffee machine". X is a random variable and X can take any value between 0 to 100cc. X is said to be a continuous random variable.
It should be instinctively clear that since there are an infinite number of possible outcomes, the probability of any one outcome is 0. We instead consider the probability of a range of outcomes. Of course P(Sample Space) = 1.