Arrow functions
Arrow Functions are a short-form technique of expressing JavaScript Functions. The MDN website discusses them in great detail and the limitations of their use.
The example that I give below also contains a "Template Literal" and shows its use in my example of "Bubbling and Capturing" of events. The useage of the Arrow Function syntax in this case was not particularly helpful as it only was used to add an event to an element using the addEventListener() Method.
I consider the use of an Arrow Function and its syntax as an advanced JavaScript technique and there are far better places on the Internet that explain their use.
I came across this when looking at Event Bubbling and Capture - the use of the useCapture parameter in the addEventListener() Method
How I saw this used first - or actually noticed it.
elem.addEventListener("click", e => alert(`Capturing: ${elem.tagName}`), true);
The JavaScript statement above also uses a Template Literal - this is enclosed using the ` character (grave accent - to the left of the 1 on my keyboard)
`Capturing: ${elem.tagName}`