Summary  
This chapter explains how to define function parameters as placeholders that receive argument values at each call, allowing you to pass data into functions and avoid redundant code.  

General domain of usage  
Geometry (e.g., calculating triangle areas)

We can pass data into functions using **parameters**:

```js
function funcName(parameter1, parameter2, ...) {
  // your code here…
}
```

A **parameter** acts like a **local variable** inside the function. However, it takes up the value of the corresponding **argument** that is passed into the function at the **function call**.


function sum(a, b) {
  console.log(a + b);
}

sum(1, 2); // Output: 3
sum(5, 10); // Output: 15
sum(20, 30); // Output: 50
sum(33, 37); // Output: 70

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- **An argument** is the actual value passed into a function when calling it:
    - Example: In `sum(1, 2)`, the values `1` and `2`  are arguments;
- **A parameter** is a placeholder inside the function definition that receives the argument’s value:
    - Example: In `function sum(a, b)`, `a` and `b` are parameters.

A function in which other functions are **called** is known as a **compound function**. A **compound function** combines smaller functions to accomplish a larger task.

Study More

How many parameters does this function have?

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Passing Data into Functions

1. How many parameters does this function have?

2. What will be the output of this code?

3. Which of the following is true?