Comments are lines that are not evaluated when the code runs. They exist just for human readers, in other words. Comments can be extremely useful when we're looking back at code we've written later on and for other people who will looking at your code.
A single line comment will comment out a single line, and is denoted with two forward slashes
console.log('Pi is equal to ' + 3.14159);
A multi-line comment will comment out multiple lines, and is denoted with
/* to begin the comment, and
*/ to end the comment.