In a shell script, comments are lines of text that are not executed as part of the script but are included to provide documentation and explanations for the code. Comments are used to make the code easier to understand and to help other developers (or future versions of ourselves) understand what the code is doing. To include a comment in a shell script, we can use the # character followed by the text of the comment. For example:  # This is a comment  Anything following the `#` character on the same line will be treated as a comment, so you can use comments to annotate specific lines of code:  # Increment the value of the counter variable  counter=$((counter+1))  We can also use comments to include multi-line blocks of documentation or explanations:  : '  This is a multi-line comment.  This comment block can be used to include  detailed explanations or documentation for  the code below.  '  Note that the `:` command is a shell built-in that does nothing, so it can be used to create a block of comments without actually executing any code. The single quotes around the comment block are necessary to prevent the shell from interpreting the # characters as the start of a comment.  Expect to come across this popular question in UNIX Scripting interviews.