Can someone explain this code

Question

function fib(num) {
if(num<=2)
return 1;
return fib(num-1)+fib(num-2);
}
document.write(fib(6));

Answer 1

fib(6)

fib(5) + fib(4)

fib(4) + fib(3) + fib(3) + fib(2)

fib(3) + fib(2) + fib(2) + fib(1) + fib(2) + fib(1) + 1

fib(2) + fib(1) + 1 + 1 + 1 + 1 + 1 + 1

1 + 1 + 1 + 1 + 1 + 1 + 1 + 1

8