Is the + operator sugar code?

In core there exists the Add trait which enables adding two types together. By default, primitive types and their borrowed forms are implemented.

If i implement this trait for my own type, type X for the example's sake, i will be able to do:

let x1 =  X::new();
let x2 =  X::new();
let x_final = x1 + x2;

So is + just sugar code? Similar to for? AFAIK let x_final = x1 + x2; expands to let x_final = x1.add(x2);

Ok. If x really is sugar code, then how does "real" addition happen? For example, what's the implementation code for Add<i8> for i8 ?

I looked at the source and... it's just this...?

fn add(self, other: i8) -> i8 { self + other } // Slightly simplified for obviousy reasons

So i8 + i8 expands to i8 + i8? I'm EXTREMELY confused. Am i even looking at the right places? Is my understanding flawed?