ELI5: Explain Like I'm 5

Jacobi sum

Let's imagine you have a bunch of toys and you want to group them into different colors. You have red, blue, and yellow toys. You count how many red toys you have and call that number R. You do the same for blue and yellow toys and call those numbers B and Y.

Now, let's imagine there is a secret formula that can help you figure out if there is a way to group the toys so that when you add up the number of toys in each group (for example, the number of red toys plus the number of blue toys plus the number of yellow toys), you get a certain number. This formula is called a jacobi sum.

It turns out that there is a special property of these jacobi sums that makes them really useful in math. They can tell us things about a certain type of math problem called a modular equation. And just like you can group toys by color, mathematicians can group numbers using a concept called modular arithmetic.

In summary, a jacobi sum is a formula that can help us figure out if there is a way to group things (in this case, numbers) in a certain way to get a specific answer. This formula is especially useful in solving certain types of math problems.