Sure, here is an explanation in simpler terms:

1. `#include <stdio.h>` - This makes it possible to use functions `scanf` and `printf` that we will use later to read user's input and print the result of the program back to the user.
2. `int fib(int n) {` - This line says that we want to declare a function with the name `fib` that takes an integer number `n` as its input and returns another integer number. A function is a way to break down the code into smaller pieces that can be re-used later. `n` is called a "parameter" of the function, and `int` before `n` means that its type is "integer". `int` before the name `fib` means that the function will "return" an integer back to the code that calls this function. `{` indicates that what follows is the "body" of the function: the code that will be executed when the function is called.
3. `if (n <= 1) return n;` - This line says "if the input `n` is less or equal than 1, return the number". "Return" in this context means that the function will stop execution and the value after the word `return` will be provided to the code that called the function as its result.
4. `return fib(n - 1) + fib(n - 2);` - The last line of the function calls the function `fib` itself twice with smaller values of `n` and adds the results together. This is called a _recursive_ call because we call the function from inside its own body.
5. `}` indicates that the body of the function ends here.
7.  `int main() {` - This line declares a function called `main`. This function is called when the program starts running.
8. `int input;` - This line says that we want to store an integer value that we call `input`. This is called a "variable": you can imagine it as a box that stores a number. You can use the value from the box, or put something else into it instead. Initially, the box does not have any value in it, and you shouldn't try to use it until you put something in it.
9. `scanf("%d", &input);` - This line waits until a user types a number on their keyboard and presses "Enter". After that, it puts the number that the user provided into the variable `input` that we declared on the previous line. `"%d"` means that we expect the user to provide an integer value and nothing else.
10. `printf("%d", fib(input));` - This line calls the function `fib` with `input` as the value of the parameter `n`. Wherever `n` is used in the function `fib`, it will have the value that the user provided. After that, it prints the result of function `fib` back to the user. `"%d"` in this context means that we want to print an integer number.
11. `return 0;` - This line stops the program execution and returns the value `0` to the operating system. This is called an "exit code" of the program. `0` indicates that the program exited successfully without error.
12. `}` - marks the end of the function `main`

To summarize, the program asks the user to provide a number `n`, then computes the `n`-th Fibonacci number and displays it to the user.

It must be noted that C is not an easy language to start learning programming with, and if you don't have any experience with programming, you should consider more beginner-friendly languages such as Python.
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