P(A or B) refers to the probability that either event A occurs, event B occurs, or both events A and B occur.
When calculating P(A or B), you will consider all the scenarios where either A or B happens, including the possibility that both of them might happen at the same time.
This type of probability is used when we want to find out the possibility of occurrence of at least one of multiple events. It helps in scenarios where there are multiple conditions or events to consider and these conditions or events may occur individually or they may occur together.
So P(A or B) indicates the probability that either event A occurs, event B occurs, or both events A and B occur.