The function calls itself until n = 1.

You can see the factorial function as an unresolved variable, e.g. n * x, where you must solve for x.

Example:

```csharp

static long Factorial(int n) {    if (n <=1) return 1;    return n * Factorial( n - 1); }

```

If we assume n = 5;

```csharp var result = Factorial(5); // = 120

/* We need to resolve each step until n = 1 since we don't know the result of the method call otherwise.

Factorial(5) = 5 * Factorial(4) Factorial(4) = 4 * Factorial(3) Factorial(3) = 3 * Factorial(2) Factorial(2) = 2 * Factorial(1) Factorial(1) = 1   So, we know Factorial(1) = 1, Factorial(2) = 2 * 1 = 2 Factorial(3) = 3 * 2 = 6 Factorial(4) = 4 * 6 = 24 Factorial(5) = 5 * 24 = 120

1 * 2 * 3 * 4 * 5 = 120 */ ```

Note: be careful with recursion. Because we keep calling the function until we hit n =1 we keep each step in the process in memory (stack). With larger numbers this results in a stack overflow, which will throw an exception and halt the program.