Probability is the measure of the likelihood that a certain event may occur or not. Probability is always between zero and 1. The probability of a certain event is 1. If today is Sunday, then tomorrow will be a Monday. It is a certain event, and its probability would be 1. The probability of impossible events is zero.

Probability is equal to favorable outcomes divided by total possible outcomes. In order to find probability, we need to determine favorable outcomes and total possible outcomes. For example: If we toss a fair coin, it will either show heads or tails. So there are two total possible outcomes.

If we need to find the probability of getting heads, there is only one favorable outcome. Then the probability of getting heads would be 1/2 or 50%.

`P(Heads)=1/2`

We can see another example. We need to find the probability of getting an ace out of a standard deck of cards.

We know that there are 4 aces in a standard deck, so favorable outcomes would be 4. We also know that a standard deck of cards has 52 cards, so the total possible outcomes would be 52.

Therefore, the probability of getting an ace from a standard deck of cards would be `4/52=1/13` .