If the probability of a 1st event happening has no impact on the probability of a 2nd event happening then the two events are independent.

When finding the probabilities for independent outcomes, we can use the and rule. If event 1 happens AND event 2 also happens, we multiply the probabilities.

We can use the OR rule when calculating the probability of either of 2 different events occurring. If asked to find the probability of event A or event B happening, we must add the probabilities.