The program defines a function factorial(n) that takes in a single argument, n.
Inside the function, it checks if n is equal to 0, and if it is, it returns 1. This is done because the factorial of 0 is 1 by definition.
If n is not 0, the function returns n multiplied by the result of calling factorial(n-1). This is a classic example of a recursive function that keeps calling itself with n-1 until n becomes 0.
The program then prompts the user to enter a number by using the input() function, which returns the user's input as a string.
The int() function is used to convert the string to an integer so that it can be passed as an argument to the factorial() function.
The program then prints the result of the factorial() function, along with some text to make the output more human-readable.
