Totlally confused...

Hello Ben! I am going to help you solve your dilemma!

First though, let's take a look at the problems in your code:

function returnValue (amount) {
  var echo = "this is interesting";
}
var echo = returnValue;
returnValue( echo + amount);

Though you have generally structured the function properly, this is not the proper way to return a value from a function, nor is it the proper way to call a returned value from a function. First let's look at your syntax for the function with parameters and a return. You will have to do something like this:

function returnValue (amount) {
  return amount;
}

As you can see in the bottom example the function is actually returning a value, in programming/software engineering we sometimes refer to functions that have a return value as a getter because it gets a value for us to use. However, by itself this getter function will not actually use the data that it gets. In order to use or store a value that a getter function will retrieve for us, we need to store it to a variable like this:

function returnValue (amount) {
  return amount;
}
var echo = returnValue("This is the value of the parameter here!");

As you can see we store the value of the variable echo as the returned value of the function returnValue (that was a mouthful). The above example will provide a correct answer to your solution, however, I believe that you need to refresh your mind on the concept/structure of a function, the parameters of a function, and return values. I will give you a quick course below:

Functions

//Below is the syntax of a function
function function_name(list_of_parameters) {
//body of a function
return return_value; //An optional return value
}

A function will allow you to perform a box of code with just one line, anywhere in your program, if you see large chunks of repeated code it is probably best to turn it into a function for easier use/readability/staying DRY (do no repeat yourself). A function can include a list of parameters that you can describe as just variables that provide information for your function to use. For example, the below function will print out your name and age, provided by the user as parameters, to the console.

function displayUserInfo(name, age) {
console.log(name);
console.log(age);
}

displayUserInfo("Dane", 20);

When I call the function (as I did on the last line of code) I will get the values:

Dane
20

written to the console.

Whatever, happens in a function for the most part generally stays in a function, and as such we sometimes need to provide a way for a function to store it's value for later use, we can do this with returns, that will not only exit a function at the return call, but also send the value that it is returning into a temporary memory location that can be later sent t o a variable for permanent storage. For example, the function below, will store the area of a square, given the length and with as parameters.

function areaOfSquare(length, width) {
 return length * width;
}

var area1 = areaOfSquare(3, 2);
var area2 = areaOfSquare(10, 5);

If we were to console.log the 2 variables that hold the value of the return, we will get (6, and 50).

Hopefully this answers your question and more. If you need any more help understanding feel free to ask. Though I do recommend re-watching the videos about functions.