‘num’ is just a descriptive name for the value you are passing into the function. It helps people who are looking at your code know what type of value the function expects to be passed in. But that name can be anything you want. That function can defined as:
function processArg(string) {
return (string + 3) / 5;
}
It will still work just fine, but it’s pretty confusing when you want a number to be passed into it, don’t you think
When you pass a number in to the function:
processArg(7)
Then num takes the value of that number. So inside the function, num equals 7, and thus the function would be doing