Probability is the chance of something to happen.
A very good example for is when you toss a coin. When a coin is tossed, you either get a tail or a head. In short, you have two possible outcomes. So the possibility of you tossing a tail is 1 in 2 or ½. The same is true with tossing a head that is also 1 in 2 or 1/2.
It would then be safe to say that the formula of probability is this:
= Number of ways it can happen
Total number of outcomes
Example:

There are 6 bars of chocolate in a box. 4 are white chocolates and 2 are dark chocolates. What is the
probability of picking a white chocolate?
Solution:
There are 6 total bars of chocolates.
There are only 4 white chocolates.
= 4/6
= 0.67

There are 3 plates in the dishwasher. 1 is a round shaped and the other 2 are square shaped. What is the
probability of getting a round plate?
Solution:
There are 3 plates.
There is only 1 round plate.
= 1/3
= 0.33

You have 5 pairs of socks in the drawer. 3 of the pairs are knee length and 2 are ankle length. What is the
probability that a knee length pair will be picked?
Solution:
There are 5 pairs of socks.
There are 3 pairs of knee length socks.
= 3/5
= 0.6

In the kitchen drawer, there are 10 utensils. 4 spoons, 3 forks and 3 knives. What is the probability that a spoon is picked?
Solution:
There are 10 utensils.
There are 4 spoons.
= 4/10
= 0.4

In an animal adoption center, a pet dog just gave birth to 10 cute little puppies. 6 with black spots and 4 without spots. What is the probability that a puppy with black spots will be selected?
Solution:
There are 10 puppies.
6 puppies have black spots
= 6/10
= 0.6