@vzn Hello :) I am an undergraduate student in applied mathematics. What's with you? :)
If we want to calculate the Fibonacci sequence fib(n) with memoization and recursion, we woud call this, and it would call fib(n)=fib(n-1)+fib(n-2), which would call fib(n-1)=fib(n-2)+fib(n-3) and so on, which would call fib(2)=fib(1)+fib(0)=1+0=1. Then it would finally resolve fib(3)=fib(2)+fib(1), but it doesn't need to recalculate fib(2), because we cached it, then it will resolve f(4)=f(3)+f(2), but it doesn't need to recalculate fib(3) and so on...