Adding comment to cell helps in understanding the purpose of cell, what input it should have, etc. It helps in proper documentation.
To add comment to a cell, select the cell and perform any of the actions mentioned below.
Initially, a comment consists of Computer's user name. You have to modify it with text for the cell comment.
You can modify the comment you have entered before as mentioned below.
Various formatting options are available for comments. For formatting a comment, Right click on cell » Edit comment » Select comment » Right click on it » Format comment. With formatting of comment you can change the color, font, size, etc of the comment.