Binding in JavaScript

Arrow functions provide a convenient and more compact way to define functions, and are particularly handy for callbacks. Just don't expect "this" to behave the same way in them as it does in other functions (once you learn how to use it!).

And "binding" just refers to the association of an identifier (name) with specific data. They are just warning you that the words "this" and "arguments" don't mean what you might expect inside arrow functions.

Here are the MDN docs for the bind() function.

This function is closely associate with .call() and .apply(), and there's a good tutorial about them here.

People used to have to deal with this stuff all the time, but luckily arrow functions have made a lot of this obsolete. For example, here's an example in the React docs.

They have this class method:

handleClick() {
  this.setState(state => ({
    isToggleOn: !state.isToggleOn
  }));
}

But because it's NOT an arrow function, it's a class method, they have to call .bind() on it before they can pass it down as an event handler to the child element. Otherwise the this would become undefined. They're doing this work in the constructor, but you also used to see it done right as we're passing it into the event handler: <button onClick={this.handleClick.bind(this)}>. Luckily, we can use arrow functions now. You can even assign an arrow function to a class property rather than using class method. So the example in the React docs from above would be this now:

handleClick = () =>  {
  this.setState(state => ({
    isToggleOn: !state.isToggleOn
  }));
}

...and you wouldn't have to call .bind(). I use arrow functions probably 99% of the time. I can't remember the last time I really needed one of the classic functions, and it avoids so many headaches with this.

this is an important concept. I'm not sure where you are in which course/track but I'm sure you will encounter some explanation of it sooner or later if you're following the prerequisites in order for the courses.