are annotations written by a user to document their code. A common package used for comments in code, apart from the traditional use of %, is the comment package.

enter image description here

\usepackage{comment}% http://ctan.org/pkg/comment
Some regular text that will appear in the document.

% This is a comment.
% Anything following a '%' will not be visible in the output
  Here is another comment, provided by the comment environment
  from the comment package. Other environments may also be defined
  as needed, to provide version-based comments.

Some more text within the document body.
history | show excerpt | excerpt history