A **function** in JavaScript is code that performs a job and is usually activated when something **invokes** it.

Here’s an example of a typical function:

```
function addThreeNumbersTogether(n1, n2, n3) {
return n1 + n2 + n3;
}
```

addThreeNumbersTogether is the name of the function you’ve created and this function returns the sum of these 3 numbers.

One thing to take note of is that a function does not have a semicolon at the end of it.

## The parts of a function

The name of a function is the word that comes right after the word “function.”

The variables inside the parentheses are each called a **parameter** (n1, n2, n3). n1 is a parameter, n2 is another parameter, and n3 is the last parameter.

We provide the numbers which are also known as **arguments**, which are the values of each one of the parameters.

So for example, invoking the function above would look something like this:

`addThreeNumbersTogether(1, 3, 6);`

The return here is:

`10`