Iterated binary operation is like a game. You start with two numbers and combine them together using a set rule. You keep playing the game using the result from the last round and the number that is left. For example, if you start with the numbers 2 and 3, and you choose the rule to add the two numbers together, you would get 5. Now take that 5 and add it with the 3 (because the 2 has already been used up). The result would be 8. Keep going until you no longer have two numbers to combine together.