what exactly is the fibonacci series code example

Example: Fibonacci series

//to find nth fibonacci number(recursive solution)
class Solution {
    public int fib(int n) {
     if(n==0){
         return 0;
     }
        if(n==1){
            return 1;
        }
        if(n==2){
            return 1;
        }
        return fib(n-1)+fib(n-2);
    }
}