In Python, you can add a comment by using the # symbol. Python will ignore everything on a line that comes after the #. But human programmers will often look for the meaning of the program in these comments.
I think it's pretty interesting that with just a single symbol you can make Python disregard any line of code that you wish. I wonder how code developers were able to dictate the rules that a coding language follows since often times it feels like we're constantly adjusting to the sundry coding rules rather than it being the other way around.