On the basis of mathematical theory, the chance of occurrence of any event is called theoretical probability.
For example if we toss a coin then the probability of a head and a tail is half half i.e 0.5.
But the probability calculated by repeated experiments and examine the outcomes are called experimental probability.
For example if we toss a coin 20 times and got 9 times head and 11 times head then the probabilities are given by
These probabilities are different what we got in case of theoretical probabilities.