A tree diagram is way to show all possible choices.
The tree diagram shows us the total number of choices. Two cones and 4 flavors result in 8 choices. Multiplication is another way to find the total number of choices: 2 x 4 = 8. Two choices in the first group (cones) and 4 choices in the second group (flavors) give 8 choices of cones and flavors. Multiplying the choices in each group will always give us the total number of possible choices.