You can select the Track Changes function from the Tools menu, but the easiest way to track changes or enter comments is to open the Reviewing toolbar. To display this, point to Toolbars on the View menu, and then click the Reviewing toolbar. To start tracking changes, click the Track changes icon on the Reviewing toolbar. The Reviewing toolbar Make the changes you want by inserting, deleting, or moving text. You can also change any formatting.
Word uses revision marks to show the changes.