Color Pattern Matchiing - What does this mod function mean?

I am using arrays and for loops to create programs that detects specific patterns in an image. I want to know what the mod function does. Why do you add m and n together? Why do you subtract 2 and what does the 8 mean in the code below? What does the mod function below mean specifically?

A(m,n)=mod(m+n-2,8)

[darova]

That is too easy for a question. Just see help: LINK

[Adam Danz]

I want to know what the mod function does

mod(x,8) returns the remainder of the fraction (x/8).

Examples:

x = 7/3 = 2 1/3
mod(7,3) = 1

x = 8/3 = 2 2/3
mod(8,3) = 2

Why do you add m and n together? Why do you subtract 2 and what does the 8 mean in the code below?

We couldn't possibly know. There isn't a universal meaning for 'm' and 'n'.