In a wooded area, you randomly select 10 trees and find that 5 are tagged. you conclude that there is a 50% probability of randomly selecting a tagged tree.

Theoritical probability is the likeliness of an event happening based on all the possible outcomes. The ratio for the probability of an event 'P' occurring is P (event) = number of favorable outcomes divided by number of possible outcomes.
Popular examples of theorical probability includes face with, say, '1' showing up from rolling a dice and head showing up from tossing a coin.

On the other hand, the empirical probability, or experimental probability of an event is the ratio of the number of outcomes in which a specified event occurs to the total number of trials.

Given that in a wooded area, you randomly select 10 trees and find that 5 are tagged. you conclude that there is a 50% probability of randomly selecting a tagged tree.

This is an example of a theoritical probability because this conclusion is not based in an experiment.