Please watch video below.
https://www.khanacademy.org/math/probability/probability-geometry/probability-basics/v/experimental-probability
What is the theoretical probability of rolling a fair die and obtaining a 1?  If you roll a fair die 6 times, how many times would you expect, theoretically, of obtaining a 1?  What if you performed an experiment and rolled the die 6 times. Will you definitely obtain your theoretical answer? Why is experimental probability often different than theoretical probability?  What do you think you should expect if you increase the number of trials, that is, rolls of the die?  Why?