Theoretical probability is expected probability of an occurrence hence the name theoretical. It is theoretical and not practical as it has not been experimented or actually become practical. Experimental probability on the other hand is probability that has been experimented- it is the result of test of probability on the actual population.
In the case above, the theoretical which is the expected probability that has not been experimented is 1/2 of getting Red cards. This probability is theoretical and therefore may change when tested. Hence the different result of 7 Red and 13 blacks with 20 cards picked when experimented
