1. Let's start by understanding what you want to learn. Since you said "explain to a 10 year old," I will explain a simple math idea in a way that's easy to understand. 2. Imagine you have 3 apples and your friend gives you 2 more apples. How many apples do you have now? 3. The rule to find out is called addition. The formula is $a + b = c$, where $a$ is the first number, $b$ is the second number, and $c$ is the total. 4. So here, $a = 3$ (your apples), $b = 2$ (your friend's apples), and we want to find $c$. 5. Add them together: $$3 + 2 = 5$$ 6. That means you have 5 apples now! 7. Addition is just putting numbers together to find out how many you have in total. 8. This is a very important math skill you will use all the time!